Is good - can definately spend a full day there. Plus new monkey house opened in July. Take own food as stuff there is expensive. Also has (tiny) adventure playground and plenty of space for them to run around when/if they get bored of looking at animals. PLenty to do still if wet as many of the animals are in themed 'houses' - have to walk between them but still.
Is expensive though - you won't have to pay for under 3, but adults is about £11, and kids about £5.50.
We have a membership there and have done since ds was tiny, so go there a lot. Don't have an hours drive though