I sometimes do relay races with my high schoolers which they tend to enjoy, and they are easy to adapt to skill level.
Do you know the game Ships & Sailors? I think it might go by different names other places, but it involves someone yelling out different names (ships, sailors, hit the deck, etc.) and the players have to complete the task that goes along with it- running to the right, running to the left, doing a partner activity, etc. It keeps the kids moving, and you could even make the various tasks more gymnastics related (push-up hold instead of just lying on the floor). The slowest to complete a task or anyone to do an incorrect task is out. For warm-up sake, you could have the kids who are "out" do some type of conditioning or stretching activity so they aren't just sitting (10 v-ups when you get out, 10 more each time an additional bunch get out; sit in a right leg split until the next bunch gets out, then switch to left). I'm sure if you google it you could find a better description. But it keeps the kids moving and most seem to enjoy it.