Cancel one, and book something else. Disney has way too many interesting restaurants to go to the same one twice in the same trip, unless the food is outstanding.
I haven't done Chef Mickey's, but I have done many of the other character buffets, and the food is never great.
Even if you book a different restaurant that has the same general characters, the change of scenery is nice.
Are you staying at CR, and/or which park do you have planned for that day?