Walterjn ghani735 I'd go with stuff like this for them. Get some motors, gears, wheels, and the like. Let them create whatever they can out of a collection of parts and no directions. There is a link here, might need to kill the ad blocker...
Par4QC professor ð€£migawd.....some of the most dangerous things in this world for small children and you are recommending them? (I don't know if I'm kidding or not, sometimesð€)