It's rare but I have seen deposits for either Wyndham Alexandria or, more recently, Wyndham National Harbor, for the winter months. I doubt you'll see much for a Thanksgiving holiday week at either of these resorts through RCI. Current bulk space bankings from Wyndham resorts go through January 2012. If any Thanksgiving 2011 weeks were deposited, they're gone.
If your spring break week is in March but not immediately before or after Easter weekend, you may have a chance there. If it's in April, extremely unlikely. April Cherry Blossom season in DC is a very popular time for Wyndham owners to book a visit. Both resorts fill with Wyndham owners and nothing's left to deposit with RCI.
I agree with the advice to seek a private exchange with a Wyndham owner. Also, if you'll be traveling into DC more than once or twice during your stay, I'd recommend choosing Alexandria over National Harbor. It's so easy to walk the half-block to the metro from the Alexandria location, plus the resort has free garage parking. National Harbor charges for local garage parking but it offers more activities if you'll be traveling with kids and you want to spend a few days at the resort itself. Either location offers plenty for adults to enjoy locally. Both are great vacation spots! :whoopie:
Wait a minute. Doesn't WorldMark have access to direct bookings at National Harbor?!??!? You may want to double-check on that. Otherwise, go for the private exchange.