It is certainly possible to do this. But I would recommend a backup plan, just in case. We parked there this last Saturday. Disney must have known it was going to be very busy that day. It was UEA weekend, I guess. We went there early in the morning so we could do rope drop. At that hour they were directing all of the traffic to the adjacent Katella lot. We ended up in the Bambi section, usually a cast member lot, with a bus pickup location set up in that area. With all of the initial traffic going to the other lot, it didn't seem likely that buses would be picking up passengers at the Woody or the Buzz/Jessie bus stops at that time. Walking from the entrance to Toy Story all the way around to the Katella lot isn't likely to be less of a walk than just going straight up Harbour to the park entrance.