The one disadvantage of this museum is it's a rabbit warren of little hallways, staircases and dispaly areas hidden round corners - I think it's because it's so old and has been added on to bit by bit. There's some parts there that haven't changed since I went there 30 years ago as a kid.
They do, however, run excellent kids' workshops during school holidays - enough to keep your child interested for a while. Displays are interesting on the whole though it can be hard to find staff to help you work out what you're looking at or how to get around.
Certainly worth a visit.