We've done it twice - once with each daughter when they were 5-6. It was great! You should have at least one parent actually on the tour, but f the other one just wants to hang back and take pictures, that's fine too. Of course, if all the adults want to, they can have a great time acting up in the MK!
The experience is different depending on how crowded it is. If there are a lot of people on the tour it tends to be just the tour. When we went with our youngest daughter though, it was just her and one other on the tour. This was really great. We rode 2 rides (Pirates and Peter Pan) and the two girls on the tour actually rode Peter Pan WITH Peter Pan! Obviously, they can only do that sort of thing when the tour doesn't have a lot of people and the parks are not very crowded.
The character involved varies - first time it was Aladdin and the second it was Peter Pan. In any case, no matter what you get a good deal of "face time" with the character at the end.
Both our daughters loved it, and the parent watching much enjoyed the other one hopping, crawling and making like an aligator through the MK!