Oh, otters are lovely :-) I went to the zoo a few months back with the little'un and we did only stay for a short while as the weather wasn't too good. I think it's easier for them to get fed up when it's like that.
If you do want to shop, the mall (Cribbs Causeway) would probably be better for you, as it's all under one roof. If you wait a few weeks, you can see Olly Murs switching on the Christmas lights... lol :D
Just behind The Mall, is a place called 'Jump'. It's a MASSIVE kids' indoor play area. It's not very expensive to get in, and you can stay for as long as you like. It's also one of those play areas where the adults can go on the stuff too. Honestly, I had an absolute blast in the house of balls!