D.S.
I have a great kids' cookbook called "Kosher By Design- Kids in the Kitchen" that I really love. A 4 and 7 year old will not be able to cook independently, but the recipes are pretty simple and easy for kids to follow, and they can do a lot of the measuring, mixing, etc. themselves. The recipes are delicious and cover everything from appetizers, desserts, snacks, etc. I use some of them as my own go-to recipes all the time!
http://www.amazon.com/Kosher-Design-Kitchen-Susie-Fishbei...
Don't worry, you don't have to keep kosher to cook from it :)