If planning on driving to MK, be sure to leave plenty of time to use TTC. You have to park, either walk to the main area or take a tram from the parking lot. Once you get to the main area of the TTC, you will have to take either the monorail or ferry over to MK. Plan on an about 45 mins from resort to MK when driving.
You can usually get into the park, before rope drop, about 30 mins before your ADR. You are supposed to show up at the restaurant podium about 15 mins prior to your ADR, so if your ADR is at 8am, and the park opens at 9, you should be able to get into the park around 7:35-7:40. THey will not let you in more than 30 mins early though.