So sorry to hear about your older brother.
Regarding the rental, this is for Disney Vacation Club properties only (Disney's timeshare), so not every property is included (Yacht Club and Swan & Dolphin are not DVC properties). With 8 adults, you will need either a 2-bedroom villa or a 3-bedrom villa. Looking at availability, there are no such rooms available at Boardwalk (or Beach Club) for a 5/18-5/22 stay. But as of my typing this message, there are 2- and 3-bedroom villas available at Saratoga Springs, Old Key West, Bay Lake Tower, Animal Kingdom Lodge, Copper Creek, and Wildness Lodge. Unfortunately, I will be unable to assist you with any such rental because I only have up to 100 points available, and the cheapest of those 2-bedroom villas costs about 150 points for that stay. But if you are interested in any of those resorts, you should be able to find someone else on this
DVC Rental Board who has a lot more points available.
(You also will have to eventually make 10 postings in other Boards to be able to send/receive Private Messages (PM). No personal info is allowed posted in the general forums, which would be required to finalize any agreements.)
I wish you the best of luck to you and your family.