We just returned from our Alaska cruise two weeks ago. You will absolutely love it! The inside passage is beyond beautiful.
We were told the cruise between Whittier and the inside passage could be choppy. But we were lucky and never had one time when we could "feel" the seas. It was smooth sailing all the way. I wish the same for you!
We were outside taking pictures all day, except when we were eating and sleeping. To go inside was to risk missing a whale, a gorgeous sunset, or other beautiful scenery.
Have a wonderful trip!