Hi again Kim,
My good friend former Moms Panelist Bret did a lot of research on this topic. You can read his answer to a similar question
HERE.
While the official word is that park transportation starts running one hour before park opening, this is not really true. There are many guests that need to get to the parks and nearby resorts for early morning events such as character breakfasts and tours. Disney wants to make sure that those guests can get to where they need to be on time.
I would stop at the guest relations desk at the Wilderness Lodge the night before your early breakfast. Explain your situation to them, but I am 99% sure that they will tell you that the WL boats will be running by about 7:15. You may find that the first boat that comes is for the Contemporary rather than the Magic Kingdom. If this is the case, I would ask the boat captain how long it will be until a MK boat comes. If it is more than about five minutes away, I would hop on the Contemporary boat and then take the monorail to the MK.
By the way, your plan is my absolutely favorite way to start a Disney day. I love being in the park early in the morning when it is relatively empty. It's a great opportunity to get family photos in front of the castle without tons of other people in the background. The CRT breakfast is great -- good food AND the princesses. PLUS, you'll be done with your meal right around 9:00 so you can be at the front of the line for the rides.
Have a wonderful time!