M.K.
I've only been there once, so I'm sure other Moms will have even better insights. But from my experience, the museum is suitable for children who are, at minimum, strong walkers. It's completely hands-on for the kids, so a child in a stroller would not have much fun at all. Also, I wouldn't take a crawler -- there are kids running around everywhere, from room to room, and it doesn't seem like the right place for crawlers.
That being said, my daughter was 15 months old (and I took along her newborn brother in the stroller/carrier). She spent most of the time in the two areas designated for younger children (2 yrs old or something like that?) Some of the other rooms were intimidating for her (the music room was pretty wild the day we went), but she loved playing in the water exhibit and with the giant "light bright" exhibit.
As for moving around, I was recovering from my c-section and wasn't moving at full-pace yet. My husband was with and did all the running after my daughter. There is no way I could have managed chasing her around on my own. It's not a huge place, but the kids are free to move from room to room. So, depending upon how active your child is, you may find yourself needing to chase him/her down.
We definitely had a good time and I'm looking forward to the time I can go back with both kids a little bit older.