We've started weekly trips to the aquarium in Ipiranga which Sophie loves. Her favourites are the albino jacares (alligators) where she can lie on the glass floor and peer at them from above (and less than a meter away which gives me a little heart attack!). Hannah's favourite is the dinosaur display which Sophie is scared of - but there's something there for everyone!
Don't go there expecting the world's best - it can be dark and claustrophobic in some places - but there are some amazing and super-ugly things to see there. The second part has a giant tank with a beautiful seal, and lots of giant fish from the Amazon. Definitely worth a trip if you are at a loss for something to do with you kids! At the moment it's $15 entry over the school holidays - and try to go early to miss the kiddie groups!
I'm going to slowly put together a list of things to do with kids here in SP. There are lots of things to do but just finding out about them is hard!