If you are using DME from the airport to WDW and you will need transportation to the airport after the hard rock I would use a town car company.
We booked a trip from ALK - HRH, and then HRH - Airport at the round trip price via Tiffany Town car last April. Most companies offer the option of an escalade/larger suv or van in addition to the traditional sedan town car and this is listed along with the prices on the websites. In addition I would confirm that they can provide 2 car seats in advance as most cars are equipped with just one. We were also able to take advantage of the free 30 minute grocery stop to stock up on breakfast, water and snacks for the room.
You could also see about a rental car, but the HRH charges a fee per night for parking !