How do we as parents keep the CI's on? That is one of the most fundamental challenges for parents of a CI kid. If the ears aren't on, then they aren't hearing.
My kids are all three ultra-active and I recognized this as my biggest issue with Taylor when she was activated at 15 months. At that time, we started using headbands with elastic loops seen into them, made by a local CI grandma. These are still our go-to method with Taylor, at age 4, as well as Lauren at 15 months.
Taylor participates in lots of sports, and so far we have been able to keep her hearing in all of them.
For dance, gymnastics, and soccer, we use our typical headband with 2 barrettes to ensure that the headband stays in her hair. This has been sufficient, except for when she does a forward roll where her head actually touches the mat ... If the coil pops off, she just replaces it and goes on.
For swimming, we use one CI and make a waterproof bag for it using a Foodsaver. There are several YouTube videos out there on how to waterproof a CI using the Foodsaver. Anyway, we put her hair in a regular ponytail and secure the bag in place with 2-3 barrettes. Then we cover her head and the bag with a swim cap (Lycra, not Latex). This works great! Diving in with flips and all, it stays in very well.
This week we are snow skiing. We do have her wear a helmet, and basically use the swim cap as we so do with swimming to hold it in place. We put on the ears with a headband. No waterproof bag is needed. We do not put her hair on a ponytail though, unless it is down low at the nape of her neck... Otherwise, the helmet wouldn't go on. So it goes in this order: headband with Ci's, swimcap, then helmet. Amazingly, she seems to be able to hear pretty well with the helmet on.
I hope this is helpful!