http://drillsandskills.com/article/10 cartwheel progressions by Roger Harrell from Drillsandskills.com
I believe in the side cartwheel as the bread and butter of all cartwheels leading into round-off. If they are this young and small, set up a station in the circuit that you can spot them. Just rocking them in a handstand with legs apart back and forth.
Learning how to kick into a handstand off either leg from gross motor learning. I have them put their hands on the floor in what I can a mountain ( downward facing dog in yoga ). Lift one leg and learn to hop on it. Kick from one leg into the air and switch it so they have to land on the other leg and kick vice versa
Straddle leg handstands against the wall. Sideways tick-tocks ( like from a forward lunge with one leg up but instead going sideways )
Do you have an 8" landing mat? Forward roll to extend into straight body. Forward roll that gets hips to vertical and extend. Kick into a handstand with one leg vertical landing on their back tight. Kick into a handstand flatback.
Stand on one side of a barrel, roll on top of it in superman, place hands down and roll out ( handstand forward roll ). Stand up a wedge mat, kick into a handstand against it ( knocking it over ) and flatback or roll out of it.