I am not sure about the hand rests.
In my experience, there will not be any wheelchair-friendly tours unless you organise them yourself. They use coaches that have three or four steps up to the seats. Shuttle buses are variable. Even in wheelchair-friendly Netherlands, we found that some had no ramp, while on others the ramp was very steep (okay going up but scary coming down). They also tend to be pretty crowded so there is less/no room for wheelchairs.
I suggest you pick the ports you are most interested in and research local providers. A private tour may be expensive, but If you can share with others, that could make it more affordable.
On the plus side, you do often get priority: At Embarkation, and at tourist sites where there can be long lines when a cruise ship is in town.
Of course, much may depend on the chair: We hired one at first, which was okay and convenient. We now have two chairs - a heavy and comfortable six-wheeler, and a lightweight folding chair that we can take on planes.