When we did our Alaskan cruise back in 2015, if you left from a US port, you had to return to that same port. If you left from Canadian port (Vancouver) you could do a one way cruise...so you did not have to float by the places you had already been.
For us, we took AMTRAK from Seattle to Vancouver, then Holland America to Seward (7 day) then rented an RV in Alaska for 4 weeks to see a lot of what there was to see (amazing look into a lot of Alaska)...never stayed in any hotel rooms.
Snorkeling, white water rafting, kayaking, Denali, walking on glaciers, visit the bears in Katmai...so much to see, you will need a lot more than 7-10 days