Accessibility of "Mayflower Steps" boat tours in Plymouth, England?

I am trying to help a blind woman arrange a trip with her daughter. She's recently lost her sight, and has not yet acquired, much less learned to use, accessibility tools for phone and internet.

To further complicate things, she has to hang on to a walker all the time, and sometimes can't do steps (depends on how many and how big the rise of each).

The daughter wants to take a boat tour from the "Mayflower Steps" but the only time available to them is on a day that Plymouth already has over half its hotel rooms sold out. (In other words, lots of people!) So we need to decide quickly yes or no and if yes, get signed up before the boat sells out. We don't really have time to hope that our web form query is answered by someone who actually knows something (or even answered at all).

Websites for Plymouth, for the Barbican, for the "steps", and for the boats did not help me determine whether there are actually any steps or anything else pertinent to this decision. I don't have all the URIs handy, except one: http://www.visitplymouth.co.uk/things-to-do/the-mayflower-steps-p1398993

So, anyone able to provide specific details on accessibility there? (or cite a useful URI that doesn't show up in web searches for "Plymouth, England" "Mayflower steps" or "boat tours" with either of the other two?)

Thanks