On Saturday Keith and I took the boys to SciTech in Frisco for the Grossology Exhibit! They LOVED it!
Everything was geared towards bodily functions: toots, burps, poops, snot, etc. There were games that launched balls into a giant nose (acting as dirt). When the nose is full is sneezes them back out. Slides and climbing walls that were supposed to be enlarged skin and the intestines. Hands-on booths for making "snot". A life size "operation" game and lots more.
Really inexpensive too (which is what we are going for right now). I believe it was $6.50 each and of course Nick and Erik were free!
You can't ask for a better place for 3 boys!