Hi there, Jeanette!
A typical meal at
Chef Mickey's will last approximately 40 minutes, at the least; that's how much time the Cast Members generally estimate it will take for the five characters to circulate around the entire restaurant. If you are committed to meeting all five of the characters at Chef Mickey's, you are looking at leaving the Contemporary Resort no earlier than approximately 9:00 AM.
You should arrive at
Epcot, barring unforseen circumstances, at around 9:30 AM, perhaps 9:45. That will give you around two hours of Park time before you need to head over to
Le Cellier Steakhouse for your lunch.
While I hesitate to tell anyone to give up a coveted Le Cellier reservation, it might be the case that after a large buffet breakfast, you won't want to indulge in some of the heavier fare that is offered at Le Cellier, which, as you know, is primarily noted for its steak.
Could you consider rescheduling one or the other? While you'll likely have time to do walk around Epcot, you might not want to indulge in the delicious offerings at Le Cellier, and that would be a shame. I might suggest switching your Chef Mickey reservation for a day when you do not have a lunch commitment. That way, on Le Cellier day, you can plan to sample all of the restaurant's best -- while having sufficient time before and after to enjoy Epcot.
Let me know what you decide to do -- and what you get to enjoy!
See you later, celebrator,
-Deborah B.