I second what some of the guys said above-have several possible plans.
One of the best trips I took last year I planned on going to the San Juans (great camping on the airport on Orcas Island at Eastsound) and 8 hours before I was to depart came up with an alternate plan to go to the Oregon coast (Tillamook, camping at Nehalem Bay-Manzaneta, then second day up the coast stopping at several airports to Copalis and back to YKM via Tacoma) due to weather in the SEA area.
Bottom line is I learned that it is best to be very flexible and also find a local pilot to ask where all the "good" spots are.