We did the tour when our kids were 6 and 9 and they both loved it as much as we did. Lots on fun information, feeding fish, checking out alligators and that special thrill of feeling like you get to do somehing that nobody else does. Worth the money.
In response to the question about walking, its not a lot of walking, but it is a lot of standing. There are spots to sit along the way, but to be able to see a lot you will want to be up for most of it.