I haven't done the tour either, but I do have one booked for May. It was $25/person (-10% with Disney Visa). I don't think that there were any age restrictions. I'm taking ds (turning 5 that day) and dd (10). Ds (13) and dh are skipping it.
It is a 2 hour treasure hunt-type tour of the Magic Kingdom. The CM that booked it for me, told me to be prepared to act a bit silly at times.
At the end, one of the characters comes out to spend some time and take the group on one of the rides.
Many have said that it was the highlight of their trip. I'll let you know in May.
Beth