Today we made catapults, using the instructions I found at Irresistable Ideas for Play Based Learning. It took about 10 minutes total to make these. I'm writing this an hour later and they are still deeply involved with their catapults projects.
I pre-glued the bottle caps with heavy-duty glue. All they had to do was hot glue the clothespin and the craft stick. Brother-Bug was able to do his own. I did Toddler-Bug's and helped Sister-Bug with hers. Them we got out the pom-poms.
Even the toddler figured out how to do his own catapult and had So Much Fun being like the big kids.
Sister-Bug played with marking where each pom-pom fell with a piece of masking tape. Brother-Bug worked on getting his pom-poms in a bin – which was way harder than he initially imagined it would be.
He also figured out that the action of the catapult and pom-pom was like Angry Birds. Once he figured that out, it became even more fun.
So right there we have math, science, and motor skills for all ages. And they're still having fun.