Mayra,
Since you will be visiting the Magic Kingdom after your breakfast, I would suggest parking at the Transportation and Ticket Center (TTC).
From there you'll hop on the resort monorail to the Contemporary Hotel.
After breakfast, you can then take the resort monorail, water launch or walk over to the Magic Kingdom. At the end of the day, you will take the monorail or boat to the TTC.
The Contemporary Hotel does provide parking for guests dining at
Chef Mickey's (give your confirmation number to the Parking Attendant), however you'll usually be given a parking pass that is good for up to 3 hours. We've parked at the Contemporary many times when going to the hotel for dinner and to shop but never stayed there longer than the 3 hours.
Enjoy your breakfast with Mickey!