OK a bit messy, but lots of fun! Make your own edible finger paint for the kids. Its cheap to make and safe to use and if theres any left over, store it in the fridge or freezer to use for another day.
Have a go at making your own Magic Rainbow Milk. Kids of all ages will love it! Magic Rainbow Milk is cheap, quick and easy to set up and if you do it outside (highly recommended!), theres not too much mess to clean up afterwards.