Subscribing, but w/ a bit of info as well. I also have an early ADR at Chef Mickey's. (7:50, and we're at AllStarSports). I've gotten comments that run the gammut on whether or not you'll be able to make it via bus. The buses generally start running an hour before park open from what I've heard, so check to see if its an EMH day, etc. But, the problem seems to arise from having to take a bus to the Transportation center and then transferring to get to the Contemporary for the breakfast.
The tip I got was to just consider taking a cab. I think someone told me it would only cost about $15, they can call for you at the front desk, and it just might be worth it to spend the extra bucks and save the stress.
Also, if you have little ones... I do... one thing I asked was: "What the heck do I do in a cab about carseats!?!" I didn't want to be unsafe, but I also didn't want to lug a carseat around WDW all day. Apparently a lot of the cab companies have cabs w/ carseats. You can request them when you call.
Have fun!