Hello. We went to Alaska in July 05, on a 10 day R/T San Fran. We were on the Regal Princess. Anyways, we had our 15 yr old son, and 16 yr old nephew with us. The weather was pretty bad, raining and cold, in the inside passage. As soon as the weather got bad, the teenagers were bored. It was too cold to sunbath, swim, and generally hang out on the decks. Most of the teenagers were lounging inside, and complaining of boredom. Us adults made the best of it, with umbrellas, and irish coffees.
If you are going on a 7 day cruise, it might not be as bad. I would consider, the activities for the teenagers on the ship. Just my thoughts. Hope this helps.