Shakes for kids

I’m looking for some advice on a sustaining type shake/snack for active kids. I have 2 daughters that swim competitively and have practice 3-4 times a week after school. I’m looking for advice on a shake or bar type snack that would provide a decent nutritional value without being too much. Not truly concerned with protein content etc, just a good all around snack. Disclaimer, one of them has celiacs disease and can’t have gluten.