How long will you be in Vancouver Canada? If you've got a day or two to spend around there I would recommend going to
Stanley Park. I haven't been there in a while, but there's lots to be done here. You can rent a bike, enjoy some of the restaurants, or just walk around...the park is huge. If your cruise is in the spring or so, check out
Granville Island. There are little markets, shops, and great food! Not to mention the great photo ops! This is a little ways out there and depending how much time you have, you may not get this one in, the
Capilano Suspension Bridge. It is one of the oldest tourist attractions in Vancouver. Mainly, it's just a shaky bridge but it was a must see for me.
As far as Alaska goes, how do you feel about the cold? Check out the
Mendenhall Glacier. It wouldn't be Alaska if you didn't check out the
Aurora Borealis. The best time to see it is between August and April, you're able to see it year round but the colors are best seen when the sky is at its darkest. You may want to look into booking one of the guided tours on the Aurora Borealis to better enjoy the phenomenon from a scientific stand point.
Since you're renting an RV you'll have liberty to go as you please....sounds great! I'm not too familiar with the campgrounds but Destination360 has some information that can help you out here:
Alaska Camping. I'm not sure if you've already done so, but there's also some information on getting an
RV Rental.
Hope this helps..Let us know how the trip went!