The lunch Buffet at the Bellagio was "a-okay", it wasn't anything spectacular. I've been told that the dinner menu is much better.
$25 to get in, 18% gratuity added to 8 or more automatically, and children 4+ are adult prices. Seems a little crazy because there's no way a kid that young is going to eat that much! Then again, I guess a buffet isn't the best place to take kids.