Karen, have not been on HAL, but went last year on Princess from Vancouver to Juneau, Skagway and Sitka. We were able to get accessible tours in all 3 ports. In Juneau I can recommend the Alaska State Museum, and the shopping area is walking distance from the ship. We had an accessible van tour to Mendenhall Glacier and the fish hatchery, as well as a botanic gardens. Take a poncho...it will probably rain someplace!
In Skagway we took the Whitehorse pass train. Train pulled right up to the ship, and is lift equipped. It is about a 1 mile push into town (doable), but about every 5th shuttle bus was accessible and they will call for one for you when needed. Shops were fairly accessible, although many had one step.
Sitka is a tender port. They lift you from the ship to a smaller boat in your chair. It can be a little nerve racking, but if you stay in charge and are directive, it works. We also had an accessible van tour here and went to the Native American center, to see the Bald Eagle recovery center, the Russian Orthodox church and Russian dancers.
Talk to the Special Services person at HAL. We have found her quite helpful for our planned cruise on the Ryndam next fall. They can tell you about accessible tours, etc. Since these ports are either American or Canadian, you should expect pretty good access, as both have very strong accessibility legislation.