There are 10 museums; we visited 5 over 2 days, and the boys loved it. They wanted to go back but we ran out of time.
Enginuity is great - VERY hands-on - a bit like Eureka but aimed at slightly older children, and not in Yorkshire, obviously!
Blist Hills Victorian Town is amazing - loads of 'explainers', and fun activities, and lots of space. The boys went to a Victorian school lesson - it was hysterical. They were absolutely terrified: thought they were going to get caned LOL.
AND it's all free for Blue Peter badge winners