"No, thank you, not right now." I love it! At least she's polite about it, lol!
I wouldn't talk about it with her (or near her when she's in the room listening) until the Wednesday before Friday Dec 31 (since that's the long weekend you are going to make the big underpant conversion) Then, on Wednesday evening I would show her the underpants (you can find training underpants that have pretty flowers and whatnot on them, they aren't all plain white anymore) and tell her "in 2 days you are old enough to say goodbye to diapers and to wear big girl underpants." Then I might read a potty book and then some other books, then off to bed. And answer her questions if she has them. if she says no, I don't want to wear those, I hate them! or I only wear diapers, or pullups, or whatever... then you can say (CALMLY) that she will be wearing underpants because Mommy and Daddy know she is big enough to wear them and do all her pee and p00 in the potty, but if she wants she can go with you to the store to choose some she likes. then do that on Thursday or Friday evening. (know where to go where there will be underpants, lol!)
Thursday night, I'd do the same thing - show underpants, in an upbeat way, and talk about tomorrow you are going to start wearing undies, it's going to be so exciting! you'll be home with me and you're going to get to be a big girl just like Mummy!
then Friday morning as she gets dressed, she sits on the potty and tries, then into underpants. TURN ON the water a trickle while she sits on the potty (every time), have a few books to read (some kids like to read books in the potty, others like you to read or talk about the day. don't leave her in the potty alone, have it be a time for the two of you to hang out, with no younger twins.
And stay close to home, take her to potty about every 45 minutes to an hour (set an internal timer so you don't forget), and don't ask "do you have to go potty now?" Simply say, "you're almost finished with this puzzle, when you are done we're going to put it up high so the babies can't get it and go sit on the potty. When you come back you can have the puzzle." (or whatever). Then you finish puzzle and follow through.
In addition to every 45-60 minutes, she is to sit on the potty before AND after all snacks and meals. Before you leave the house either for a walk, car ride or play in the yard, also the SECOND you come back into the house - seriously, drop those groceries on the floor unceremoniously and hussle to the throne, because sometimes you've been holding it and hit that nice warm air, so close to the toilet, and you can't hold it anymore!
then before naptime, after naptime (even if her nap pullup is wet), then before bath (if she sits on the potty while you draw the water for bath and she'll probably pee), before bed, first thing in the morning, etc. etc. etc.
Lots of times.
and get ready to do lots of laundry. she should wear EASY on/off pants or a dress with NO TIGHTS (those are impossible to remove fast). But (I'm serious) buy about 24 pairs of underpants. you'll use them for a long time, but you don't want to have to go back to a pullup because you ran out of dry undies - that's a huge step back. like these: thick underpants because they will hold a little bit of pee and BM but they aren't miracle workers, she'll still get wet! http://www.amazon.com/Gerber-Training-Pant-Pack-Months/dp/B003BIFOK4/ref=sr_1_2?ie=UTF8&qid=1324352967&sr=8-2
put her in a pullup when you leave the house, even for a long trip to the grocery store, etc. She cannot wear pullups sometimes and underpants other times - it's all or nothing! (although I personally wouldn't take her on long trips that first weekend, or even for a week or so after, she needs to get good about holding it long enough to get to a toilet, etc.)
Don't expect that she will tell you she has to or ask to use the potty - if she's dancing around, twisting around, or acting hyper - like running back and forth from kitchen to family room for no reason, she's probably trying to hold it. so say "time to go potty" and then take her. you can't ask at this stage, or expect them to tell you (that's a few months from now when she's basically toilet trained).
you're right, you've waited a while and this means that she is TOTALLY physically able to do this, she's old enough, etc. - but of course, she also knows it's a huge PITA to go to the potty, take your freakin' clothes off, sit, pee, wipe, pull up all those clothes, wash your hands (oh, the horror!), then come back and find that your twin siblings took the legos you were playing with. or the friends in your preschool did. or whatever. MUCH easier to just go on the fly and keep on playin! (lily's twins were younger, they didn't know about this so they were thrilled to go potty.... that's why it's easier younger if they're willing).
you can do the naked thing at the beginning if you wish, although I do think your daughter might need to have squishy pee socks, squishy shoes, soaking pants, sodden undies, etc. to drive the point home.... And if she has an accident, you should help, comfort if she's really upset, but not do all the work - she does need to pull down the wet undies, pants, and put them in the laundry. otherwise, she's not being responsible for her decision not to go to the potty. Again, this is because she's 31/2 yrs old and older - I'm less hard lined for 2 yr olds, as they are developmentally younger.
And, when she does stay dry, you talk about how proud, just like Mommy and Grandmommy, or whatever, and she can certainly call Grandma or Dad, or Babysitter, to tell her the big news, etc!
you may find that she needs some extrinsic encouragement in the form of 'when you do #1 or #2 on the potty, you get a sticker on your chart.' When you have 5 stickers, we can go to the ice cream store for an ice cream cone all by ourselves, just you and Daddy/Mommy." then once she's had the ice cream cone, the sticker chart is wiped clean and she starts building towards 5 more stickers... etc. this means she isn't getting a prize for every litte event, but rather for continuity, the doing of it over multiple times. Again, I don't usually think extrinsic motivation is necessary or a good idea, but she's older, so you may need to pull out all the stops.
Eventually, you'll move to when you are dry 5 days, all day, you and I are going to do something special that you know she likes (go to the aquarium alone, or for a walk in the woods just her and Mommy/Daddy, whatever).
I'd keep her in pullups (not diapers, those are going to be removed from the premises Friday morning) for bedtime and naps for a while longer, or at least at bedtime if not during naps.
I'd buy a potty chair she can sit on the floor and have her feet flat on the floor, so she isn't dangling on the real toilet. But also get a stepstool so if she chooses to sit on the real toilet she can put her feet on the stepstool comfortably (not too tall, not too short of a stool) because to have a BM you have to be able to have your feet on the floor and bear down, or stay balanced. (BM-ing mechanics 101)
Keep a positive attitude, do NOT shame her "I can't believe you had another accident" - rather, "remember, you need to pee in the potty so you can stay dry and comfortable."
ALSO, while we're kinda assuming she's going to be resistant, she might not be once she realizes you are an immovable force and you've made this decision for her. She won't be able to say no thank you and get out of undies, and she may be happy for the decision to be made for her. so go into this with a positive attitude!
and drink some gin and tonics after she goes to bed, you'll need 'em!
Rhm, i'd start having your son sit on the potty with no diaper on when you draw his bath, when he has a dry diaper after nap, whenever you're in there for whatever reason, or just cuz. It's now that you should be getting him used to sitting, not worrying about falling in, perhaps accidently actually peeing (and wow, he'll eat up the praise you heap on him), and overall just getting in the practice of it. then when he's older you'll start having him sit on the potty at all the times above even though he's in a diaper still so he gets into a 'potty frame of mind' (before nap, meals, going outside, after nap, meals, etc. etc) before you take off the diapers and go to underpants. Think about how wonderful it would be if you had twins and a 2 yr old who didn't need diapers except at nap and bed, how freeing!