Personally, I would drive. I think Beach Club will give you a three hour parking pass, so you may have to drive to the Epcot lot vs just going in through the IG, but I think you will be able to leave POP much later to get there on time.
Plus, if it is crowded, going in through the front, I think, gives a better advantage to hitting Soarin' or Test Track first. Even when I stay at Beach Club, I still drive over to the front lot if I am going to Epcot 1st thing in the AM.