Hi Linda,
I am pleased to tell you that Chef Mickeys at Disney's Contemporary Resort does indeed participate in the Disney Dining Plan (valid for arrivals 1/1/2011 - 12/31/11)
My family ate here just a couple of weeks ago and it was so much fun!
Other restaurants which also participate in the Disney Dining Plan and where you are likely to find Mickey Mouse include:-
The Garden Grill restaurant featuring Chip 'n' Dale in the Land Pavillion at EPCOT
Ohana's Best Friends Breakfast with Lilo & Stitch at Disney's Polynesian Resort
Donald's Safari Breakfast inTusker House Restaurant at Disney's Animal Kingdom
You can find details
HERE of all the restaurants within Walt Disney World which currently participate in the Disney Dining Plan.
I would recommend making an advanced dining reservation as soon as you are able to as Chef Mickey's is a very popular choice for many guests. Reservations can be made up to 180 days prior to your visit.
Have a fantastic time and don't forget to have your camera and autograph book at the ready!