We saw
Bodies: The Exhibition (same as Bodies Revealed, I guess-both are listed on this site
http://www.bodiestheexhibition.com/) recently. It was great, very educational, really neat thing but I don't think my kids (ages 8, 6 and 4) are quite ready for that yet. It's intense, and knowing my kids I thought the 8 and 6 year olds would find it a little creepy or scary (the 8 year old has an anxiety disorder and you never know what'll scare her; the 6 year old gets creeped out by skeletons). While I'm not sure if it would frighten my 4 year old I just don't think she'd have the patience for it. It really was a quiet, hushed, almost reverent atmosphere (with lots to read, and she'd have to be held up in order to actually see most of the displays)--I couldn't see her not being impatient and at some points disruptive. I think if it comes around again in a year or two, we'll consider taking at least the older two kids.
My kids love learning about bodies, too, and we have a book all about the body and how it works (with illustrations of all the systems). They also like to go on BrainPop, which has some great videos and explanations regarding how the body works. So far this has been enough for them in terms of satisfying their desire to learn about the body.