Themes for summer school

I've decided to go with theme units, at least with my fourth grade students.

We'll start off with the farm, and then do camping next week. I'll bring a tent in from home, make up a fire, and bring in camping chairs, sticks, "roast marshmallows" eat smores, etc... We'll work on writing about both topics.. reading stories about both, and maybe acting out a play. I have one about farmers anyway.

For the final week of June I'll take some time and think about the theme for that final week. I'm considering allowing them to choose a theme, but I may not. It'll depend on cooperation, and enthusiasm.

Any ideas from the readers on a theme for the final week Any sources you know of that I could look at????