Well it would be easier to take the boat over to Fort Wilderness. BUT, you need to consider your seating time for HDDR and MK closing time. You don't want to miss the last bus or boat back to MK. If you have the earlier seating and the parks are open until at least 9pm I would think you could bus or boat over. Otherwise, drive the car over and follow the signs to Fort Wilderness. You will have to park at the outpost out front and then take the internal bus to the back of the fort where HDDR is located. The marina and bus stop are right at the HDDR area.