Give the kids a Canvas and let them create! (It doesn't need to be fancy!)
This week I bought a file cabinet. Presley played all afternoon inside the box while I organized piles, and piles of papers! When Ethan got home from school I asked them if they wanted to paint the outside of the box. They were so excited. My kids love art and they love projects. We sat down and they each painted a side of the box. Even I painted a side of the box! It so funny but this box provided hours of entertainment for my kids and they were so proud to show Daddy when he got home what they had made.
You don't need special supplies, just a box and acrylic paint and maybe a bed sheet to cover the ground! Grubby clothes would be good too!