I've never had a problem getting off a bike, regardless of my facial expression. We did FTP tests the other day, and I must say I was not smiling at the end of that.
I think a fused ankle would make swimming a little weird, but not terribly so. Might actually help on the bike.
Cycling is a gear/gadget disaster, so be warned that if you are a gear geek, it will get expensive. Swimming is the opposite - you can only take off so much before they kick you out of the pool.
