MiceRNice, I have to add that another advantage to the Alaska ABD is that each day you are doing the equivalent of 2 or 3 excursions, much more than you would be able to arrange with
DCL or on your own. In both cases, you would have to make your way back to the ship, and then catch a second excursion, or even a third. The DCL system won't let you book excursions that they think are too close together. Since ABD is coordinating everything, including all the transportation & meals, it all works seamlessly, and you will get to do and see far more each day than most other people.
And the number of people on your excursions will almost certainly be less than you would see on most DCL excursions. And you get priority disembarking in the ports.
Also, since you are doing all your excursions with the same people, your son will have that continuity of the same kids at all of the activities, and hopefully even on the ship.