I agree with the poster who recommended doing low-level/pressure activities together rather than insisting on the classes.

And it sounds like a great idea for you to sign up for the classes yourself, OP. YOU are interested in these things. Focus on and enrich yourself instead of anxiously pushing your quite-young children to do things they aren't interested in. It's fine for young kids to not be in scheduled activities.

It is understandable if swimming is a must-learn for your kids, though.

OP, do you know how to swim and ride a bike? If not, take the lessons with them, or right before or after them so they can watch you too. If you do, take them swimming or biking or just normalize them as activities to enjoy and not fear.

For al the other stuff, just don't sign them up if they're not interested. I'd never learn rock climbing just so that my kid could learn.

OP try reposting this in the kids with special needs forum. Them not wanting to do anything with water/foot not touching the ground could be a sensory processing issue.

I agree with a PP. Swimming was a non-negotiable for us from a safety standpoint. Bike riding is also a useful skill to know. I didn’t encourage rock-climbing because I don’t want them to take it up seriously.
There must be something your kids enjoy. Have they actually tried out these activities before they decided they didn’t like it?