That is the correct way, but the BBQ is at 6:30 pm. You will be cutting it VERY close if you get to your resort at 5:30pm. You will need to check in to the resort. (The lines to check in at the Values can be quite long. You'll need to get your actual paper tickets for the barbecue which is at a different desk, then wait on a bus to MK, then wait on a boat to Ft. Wilderness.
You really need to get to Ft. Wilderness by 6pm, which with your 4pm flight arrival time is cutting it waaaay to close. Even if you take a taxi to Ft. Wilderness, you would then have to take an internal Ft. Wilderness bus to the BYBBQ.
Since this is a prepaid meal, I just wouldn't chance it on arrival day with that short of travel time.