Not sure what kids club activities they offer, but bear in mind that alaska cruises cater to an older demographic. I went on one a couple years ago and probably saw 1 or 2 kids. Most folks were retired folks 50+. So don't expect there to be a large flock of kids for yours to play with. Also most of the things to do on an alaska cruise revolve around enjoying the scenery. Your kid may or may not like that kind of activity.
There are cruises that leave from San Diego, which I think is within the 3hr plane ride requirement. Also Disney has cruises that leave from Los Angeles that go down to Mexico.