Although it may be an inconvenience to not have your family at the same resort, Palm Desert has the unique benefit of having three Marriott Vacation Club resorts in the same resort area. In so far, I'd suggest that you quickly add Desert Springs Villas I and Desert Springs Villas II to your request. If you are willing to accept a one bedroom villa, I'd make that known to II ASAP. My personal opinion is that the likelihood of a confirmation in to a two bedroom villa at Shadow Ridge is low (and further lowered if you limited the number of check-in days that you'd be willing to accept).
A few thoughts:
Thanksgiving week is a very high owner occupancy week at the Palm Desert resorts. The owners who purchased in the early days at Desert Springs I and II were taught by the sales people to occupy or rent their master suite when they can, and trade or rent their guest suite (or some combination of the above). Between the high owner occupancy, and the number of owners who lock off their villas, I'd speculate that the number of two-bedroom villas that II gets for Thanksgiving Week is relatively low.
It seems to me that there is a surge of deposits to II at the one year in advance point, and that inventory trickles in during the remainder of the year. Because you started your exchange in February, and not November, you missed that first surge of deposits.
Without knowing what Silver Season week you exchanged from Summit Watch, I wonder if the exchange power of that week may be playing into the equation. Also, without knowing when you deposited that week, I wonder if the value of your deposited week diminished because you deposited it less than a year in advance.
Being that you are now inside of 60 days, I'd think that those owners who were trying to rent their Palm Desert weeks, and who were unable to, would have deposited them to II at no later than the 60 day mark.
Good luck.