Beaches-Oregon (no contest)
Mountains-Toss up (in May the mountains won't be very hikable though, due to snow)
Wineries-Oregon (Yamhill/Carlton area, Walla Walla, WA is a close second though)
Breweries-Oregon (Tight race but the nod goes to OR)
If they decide Washington, a few days in the San Juan Islands is well worth the effort.
If I were to plan something for them, I'd fly them into PDX, pick up a car, head west to Astoria, then spend the bulk of their time driving south down Hwy 101, skipping Seaside. 4 or 5 days of beach life, then inland to the Willamette Valley for a couple days of wine tasting then back to PDX to fly home. Despite the naysayers, OR and WA are worth visiting.
