It sounds like you want to eat them in a restaurant, correct? H says Chuckanut Manor is well regarded, as is the LaConner Seafood and Prime Rib Resto. I would definitely call these places to ensure they have Wa dungenness. We have no personal experience with these two places.
My only other suggestion would be to buy some at Costco or a supermarket and steam them at home.
Oh and the Swinomish Casino near Bow, with a restaurant named the 13 Moons. They offer crab cocktails, Crab Louie, crab cakes, and crab crusted ling cod. Also crab Mac n cheese. Again, no personal experience here. Good luck and please let me know if you find a good place. Enjoy your visit as well, even though it sounds bittersweet. Hope everything goes smoothly for you!