My husband and I (no kids) really found our Mickey amusing. He would tell silly jokes, remind us about parade times, and give us interesting facts about the parks. I personally did most of the Mouse carrying and did not find him cumbersome to carry-- the clip worked well and I frequently palmed him. You would definately need to hold him to your ear in all parks except the Animal Kingdom (I guess its quieter there)-- but again, this was not a problem for us.
There were some glitches with the fellow-- he was confused about where we were a few times (telling us about a parade in a park we had already left-- this seems like a common problem). But we were at the World for 2 weeks, with 6 days in parks-- and didn't leave home without our Mouse... He will be joining us for a quick trip we are making in December. And another quick trip in May...
However, if your teens are prone to finding things lame and if they embarass at corniness, you might want to skip the Mickey. He can be quite a chatterbox and it would be e bummer if the mouse caused family stress...
Beatnik