I have a lego crazy boy at my house! It was a Christmas full of lego kits!
Well lego has it's own Creationary app and it's free! The newest version has a 2,3 or even 4 player mode and you can play connected to apple tv! How cool is that? There are 4 different modes to play in. My son even likes to take screen shots of the lego creations and build them himself with his own lego!
Lego also has about 5 other apps that are all free for your "lego crazy" kids! I have never used any of them but they are all linked from the itunes page for Creationary! Enjoy!