I have found that the most essential thing for my children is for me to be receptive to what they want. My kids are in swim classes because I agree with you that it is an essential skill. They currently are not doing anything else, but typically I would let them have one other activity. This way they can choose to try something they think they may like. They can explore what is out there, and maybe eventually they will settle on something they want to continue to do. My son has pretty much settled on basketball and it is exciting to watch him play and great for him to learn team concepts. I know your kids are younger than mine and one class is more than enough in my opinion for babies. Toddlers have fun doing most anything, so as long as you provide many activities for them, that is way better than any class can provide. Dance with them, cook with them, explore with them.