Hello Anita! Welcome to the Disney Parks Moms Panel.
I can tell from your inquiry Anita that you have a firm grip on the options available to you on the Endlessly Magical morning you have planned.
With the Magic Kingdom opening at 8:00 am on the day of your Advanced Dining Reservation at Chef Mickey's, the
monorail will begin running between 45 minutes to an hour before opening. This may make it a pretty harried rush to get to Chef Mickey's in time for your Advanced Dining Reservation, but it is doable.
Chef Mickey's is across the main hall from the Monorail depot, so it will all depend on the time your monorail trip departs the Ticket and Transportation Center.
As long as you make it on time for your
Advanced Dining Reservations, you are a 10 minute stroll to Magic Kingdom, which is a definite bonus!
Since you are driving, you could drive directly to Disney's Contemporary Resort (tell the Cast Member you have a reservation for Chef Mickey's, there is no charge), however there is a 4-hour window for how long a Guest is permitted to park at a Walt Disney World Resort hotel for dining. This option would require you to drive back to the Ticket and Transportation Center after you dine and take the monorail or ferryboat to the Magic Kingdom from there.
I recommend the latter option as it allows you to control when you arrive at Disney's Contemporary Resort, removing the stress that a missed monorail may provide while still giving you an opportunity to experience the "highway in the sky" monorail trip to Magic Kingdom.
It's a choice between convenience and experience!
~Todd