With my young clients, I let them play their own music. Jump rope is a good cardio exercise and fun. I do a balloon workout (you can google it) and also a towel workout. Footwork ladders are also fun. I use partner exercises and have them all on a separate small piece of paper. The client “draws” one and that’s the one we do. This is repeated for a full workout. I vary the workout props – resistance bands, BOSU, free weights, TRX. Good luck!