Not sure about the discount question, but wanted to let you know that you can get the plan for the marina here is the info on that:
Family Plan- $239 plus tax (non-refundable) - Includes use of boats and bicycles for up to 5 Guests for 10 calendar days. This offer is valid only for registered WDW Resort Guests. Boats/bicycles are available on a first come, first serve basis. Boats/bicycles included in this offer must be rented from the Wilderness Lodge Marina only. Please call or visit the Wilderness Lodge Marina for further details. Other restrictions may apply. (Cruises and excursions are not included.)
Captain's Plan- $125 plus tax (non-refundable) - 4 hours of rentals (any combination) of boats and bicycles. This offer is available to all Guests, and boats/bicycles included in this offer must be rented for the Wilderness Lodge Marina only. Boats/bicycles are available on a first come, first serve basis. Please call or visit the Wilderness Lodge Marina for further details. Other restrictions may apply. (Cruises and excursions are not included.)