Hi Tina,
I am a HUGE fan of Disney tours! Both of these tours take place during regular park hours and reservations can be made by calling 407-WDW-TOUR.
Mickey's Magical Milestones Tour begins at 9:00 a.m. and lasts approximately 2 hours. It is held on Mondays, Wednesdays and Fridays. As of 7-7-10, the price is $26.63 per guest which includes tax (always subject to change without notice). Magic Kingdom theme park admission is required and is not included in the price of the tour.
Disney's Family Magic Tour begins at 10:00 a.m. and lasts approximately 1 1/2 to 2 hours. This tour is held every day. As of 7-7-10, the price is $34.00 per person which includes tax (again always subject to change without notice). Magic Kingdom theme park admission is required and is not included in the price of the tour.
Both are a lot of fun but if I were choosing between them for your DD12, I would choose Mickey's Magical Milestones Tour. Its geared for those a little older as your host tells the how Mickey was created and has evolved over the years which may not hold a younger guest's attention as well as the Family Magic Tour.
Disney's Family Magic Tour is a lot of fun - I'm a big kid at heart so I really enjoy it but some tweens may feel they are a little too old for it. That's a tricky age because some 12 year olds may not get into the spirit of searching for clues with the younger guests.
Whichever one you choose, you can always do the other one on your next visit. Wishing you many magical memories :-) Allison