My wife has MS and has problems walking. We have a transport chair that we use most of the time. When we were in Juneau two years ago we took two tours which were great. Provided that you can take some steps onto the Bus, both of these tours are great and everyone on the Princess team helped out.
We took the Mendenhall/Fish hatchery tour in the morning and thern the Helicopter tour that landed on Mendenhall Glacier in the afternoon.
It was wonderful to see Mendenhall from the park headquarters perspective and then fly to the top of it in the afternoon and get out and explore. The folks at Temsco helped her up into the helicopter seat when we took off and helped her out when we got to the Glacier. The guides went overboard to take care of her and help her out at the top. It was the tour of a lifetime for her and she was overjoyed by the extra effort of everyone. If you can walk abit it shouldn't be too much of a problem. Just don't be rushed and take it at your own speed and the folks at the helicopter service will make it happen.
This fish hatchery was great also, we saw plenty of Salmon jumping up the fish ladders and in the bay, with many eagles watching for their chance at lunch.
Good luck and enjoy, Alaska is great. If at all possible get a balcony cabin, the ablity to sit out on the balcony is well worth the price..