Open each day with some fun acting exercises. On day one, have kids pick a script (15-minutes in length) (maybe in small groups for the older kids), and begin learning it. On day two, following quick activities, keep practicing skit. On day three, one last rehearsal session, followed by a quick performance for parents at end.
Scale with session length. One-hour sessions as described. Two- and three-hour sessions could be a 30-minute skit, but with more acting activities.