taipei zoo is fun, but don't go on a rainy day!
there's a miniature museum that we went with our 21 mths old over christmas and he had a great time (it's not too big but you can spend some time 'stamping' the collection book
can't remember which floor, but at the taipei living mall there's an entire floor dedicated to children, older children can dress up and pretend to be a certain career and walk through an entire section of big airplanes, fire houses, etc so that they can play pretend (i think this is called babyboss or something). younger children can play in their ball pool/slides section...