We spent a couple of hours on the Polly Woodside. Our five year old loved being part of the crew (Sandra the facilitator was amazing!) - you must, must do a crew call if you have young kids! We learned a great deal and were incredibly impressed by the efforts of the volunteers that restored and maintain the ship. The little museum and video are brilliant at contextualising the ship.
We are UK National Trust members so got in free. We got on a tram over to the old gaol and spent the afternoon there - a perfect day! The old goal is a little less suitable for younger children than the Polly Woodside.