Best Cruise Line for a 10 year old
 

Taking a family vacation with a 10 year old grandson to Alaska on a 7 day cruise from Vancouver with a 4 day extension in Anchorage area.. Which cruise line should we consider? And what land excursions would interest a ten year old? He likes most activities. Thanks.

Try Disney Cruise Line.

cruisecritic.com has a lot of good info.
I don't think Disney does Alaskan land & cruise deals. I couldn't find any on vacationstogo anyway. But, you can cruise with Disney and then arrange your own land tours.

Disney doesn't operate one-way cruises between Vancouver and Seward or Whittier, just round trips. They're also usually very expensive compared to others.

Most of the major cruise lines offer on-board programs for kids - "clubhouses" etc. I would choose a cruise line/ship based on itinerary rather than on some imagined kid-friendly programs; the one-way cruises are so port-intensive that there won't be all that much time on the ship for the activities to matter much. I would pick a cruise that calls at Glacier Bay, and ideally one that also calls at the Hubbard Glacier.

As for what port activities and excursions, well, that depends on your itinerary and on your budget. Many of the ship's excursions in ports can be replicated more cheaply by booking them yourselves, or - my preference - just going on your own. For example in Ketchikan you can ride the city bus to Totem Bight State Park - totem poles, Tlingit longhouse, rain forest walks - for a couple of bucks, vs. probably $50 - $100 per person for the ship's tour that will basically cover the same things. In Juneau there are whale watching excursions, or you can just walk around Alaska's historic capital - once you're a couple of blocks from the ships the town will feel more like any other small Alaska town. Or in Skagway, rent a car instead of paying a small fortune for the White Pass train (with thousands of your fellow tourists) and drive yourselves up into the Yukon, stopping at a tiny subarctic desert near Carcross, or heading a few miles farther up the Klondike Highway toward Whitehorse and stopping at an old ghost town (Robinson Roadhouse) where it'll just be you and several dozen seriously annoyed marmots protesting your presence.

I'd pick a cruise that ends in Seward (all the lines except Princess) and then stay a day to do a Kenai Fjords cruise before heading into Anchorage. With just four days after the cruise you won't have enough time to go to Denali National Park, so pick activities that can be accomplished as day trips from Anchorage. Google Hatcher Pass and Independence Mine, "26 Glacier" cruise out of Whittier, Alaska Native Heritage Center, Alaska Wildlife Conservation Center, Alyeska gondola, Eklutna Native cemetery, and Anchorage coastal trail, for starts. Also I'd save some money on cruise excursions and take a flightseeing trip out of Lake Hood in Anchorage for a never-to-be-forgotten experience. https://www.flyrusts.com/

The message boards at Cruise Critic - https://boards.cruisecritic.com/ - offer all the information you'll ever need on the subject.

Check out tours
 

Check out tours
whale watch Alaska is good

Check out tours
 

Check out tours
whale watch Alaska is good

OP doesn't say when, but after this year Holland America is moving to Whittier as well. HAL and Princess are both part of Carnival so I'm guessing they're saving money by combining facilities.