Jell-O is always fun for kids to make. You can make a rainbow Jell-O cup. It does take a few hours. Get all the colors of the rainbow and some sour cream if you want to add some fun layers. Boil one color and keep half of it out to mix with one cup of sour cream, pour the first layer into the cups and place it in the fridge, after about 30 minutes you put the sour cream mixed layer on top of that and just keep repeating until you have a colorful rainbow Jell-O cup!