The parks open at 9, so depending on what time you want to be there. As far as parking goes, for MK park at the Ticket & Transportion Center (TTC), you could also park here & take the monorail to Epcot. (kids would like this) Buses also go to AK & MGM from the TTC, but, that could take a while. For AK & MGM I would just park in their lots. You only have to pay once per day, so you can hop from park to park in your car. The earlier you arrive, the better parking spot, but with the trams you never have to wait long anyway.
You might get some better options from someone else, but this is what I would do if I stayed off property.