We just recently moved from Whidbey Island back to Pensacola, FL. I absolutely LOVED it here! I would hike the Seaview Trail on base all the time (3.2 miles RT) as well as the waterfront trail that starts/ends @ Windjammer Park. Yes, the temps are much cooler in the summertime than most areas, but you can't beat the little to no humidity!!! I'm missing it a lot right now :(
We Love the tide pools at Double Bluff when it is an ultra low tide. Fort Casey is a must see! And, Deception Pass is beautiful! I think the state park has a nice swimming area to check out. (also see my review on the Rhododendron Gardens on Whidby Island.)
There is a lot to do and see on this Island, check out the website for more information.