On the website there was a long list of activities at Lego Mania. We expected there to be Lego stuff throughout the museum, in fact it was hard to work out where we were supposed to be initially. Eventually we found a corner with Lego stuff.
There was a guy making a very impressive Lego model of Basing House (a tudor mansion.) Very cool, but not much was built yet, and it's not really a spectator sport. The really big bags of Lego bricks were impressive. A time-lapse video of the build so far would have been good.
There were a few small display cabinets with custom minifigures and old toys on display, and a few information boards to read. There was a big cardboard Lego figure that a child could put their head through and get a photo of them as a minifigure (quite fun.)
And there were lots of tables with Lego and Duplo for kids to play with. They did enjoy that, but its something they can do at home and after a while most of the Lego had been built with and you had to take things apart before you could build anything.
There was also a small TV screen where one child could play Lego Star Wars. (My 3 year old loves to watch Lego Star Wars so he enjoyed that.)
It was hard to spend much time at this area though we did our best to make the most of it. We spent some time building Lego models, but we do that at home most days! One cool thing was the range of colored bricks available, there were lots of colors we haven't got at home.