We were invited there on Sunday to sample this:
And although we were among the very last people to leave the museum at closing time, there's so much going on that at the end of the day there were still some things we hadn't seen or done.
As you'd expect during half-term, it was busy - but not excessively so. The queues for the rides were all quite short; there was plenty happening and you were never standing waiting for anything for very long. I was impressed (as you might expect) by the fact that there were baby-changing facilities in the mens' loos (I don't get out much) and a play area outside for a three-year -old to expend some of the energy pent up on a two hour car journey.
Of course, it was a small boy's dream day out. You can ride on trains large and small - there's even a little land train to take you into York - stand on the footplate, sit in the fireman's seat and even walk underneath one enormous locomotive. And if trains aren't quite your thing (as they aren't for Sally) you can even join the Shuttle for a mission to the Space Station.