The Discovery Museums will offer free admission on Friday evenings this summer, starting this week and continuing through Aug. 30. The Children’s Discovery Museum and the Science Discovery Museum will be open until 8:30 p.m., with free admission beginning at 4:30 p.m. Families are invited to bring a picnic and enjoy the museums and the outdoor exhibits at the complex, at 177 Main St. The museums will collect donations for the Acton Food Pantry and Open Table of Concord and Maynard on those evenings. For more information, visit www.discoverymuseums.org. Full story for BostonGlobe.com subscribers.