Hi Tracy,
Disney is not a place where cast members will have their hands out for tips. You'll need to tip waitstaff, bartenders, bellmen (or women), parking attendants, and possibly the housekeeper for your room. Other than that, I can't think of anyone that I've tipped at Walt Disney World. To the best of my understanding, cast members in roles other than the ones I've listed are not allowed to accept tips.
I've taken the Family Magic Tour twice, both my children and I had a wonderful time. Although our guides were lovely and energetic, we did not tip them, nor did anyone else on either tour.
While I applaud your instinct to reward the great Disney cast members, when taking the tour you can go ahead and concentrate on having fun without worrying about tipping.
If you'd like to provide something positive for your guide, a wonderful gesture would be to write a note of commendation. All guest suggestions or comments should be directed to the Guest Communications Department. They can be reach through the mail at:
Lake Buena Vista, FL 32830-0040
The e-mail address for Guest Communications is:
wdw.guest.communications@disneyworld.com.
Be sure to note the cast member's name and the date/time of the tour you took. Guest feedback can play a big role in employee evaluations and promotions at Walt Disney World. Positive guest comments can be a great benefit to the cast.
Enjoy your tour!