RAF Museum
Kids seem to love big things in big spaces. My daughter enjoyed running around in the first hall of the expansive hanger with all the airplanes in it at the RAF Museum London, before she even realized we were in a museum. Plus is was freezing cold out today and the hanger was much warmer than the parking lot.
There are many, many planes, copters, some boats even at the museum. There is a good mix of aircraft from all over the world if you have a chance to check them out while the kids are dashing around/behind things.
There is an interactive area for kids, Aeronauts, but probable better for 7+ as it is technical about flying and there are some simulators that kids need to be about 1.5m to use (they also look pretty active=scary for tikes). Although young kids can be easily amused by yanking at various flight sticks and getting wind blown in their faces by some strong fans.
The aircraft are very impressive. Jet, bombers, old-time planes in many variants are there to be seen. We were there for 1.5 hours, and we didn’t even make it over to the Battle of Britain hanger–will have to go back for that–and the kids left exhausted after running around. The place was not too crowded, but I would guess that even on a busy day it is less packed than the Natural History Museum (but even the tube station during rush hours are less packed than that place). So I would say that if you like planes that you will have as much fun here as your kids. And it is all free and the cafe was reasonably priced.
(make note to self: remember about airshows– Duxford , find more)
More info here: RAF Museum London
