Tassie has lots of cool stuff for kids - we were there early last year. Try a harbour cruise in Launceston, a visit to Cradle Mountain (even when the weather is off it is amazing, even from the car park), Wings Wildlife Park (as mentioned above), the Salamanca Market in Hobart (Saturdays), the museums and galleries everywhere. Buy a copy of The Entertainment Book (google it) and you'll find it pays for itself in no time.