If you are using a travel agent use them for this; if not email and follow up by snail mail to the address for passenger questions. Ask for simple pictures of the tendering area. We went on Crystal's Serenity Northwest Passage cruise from Anchorage to NYC complete with our own ice breaker through a good deal of it. I know I did not have the balance for a RIB but my husband did and a table mate, retired Navy Captain with a posterior cervical injury while mine is anterior, also did once. He can walk well on flat services but brought a lovely old silver topped cane just in case. After getting back from a rather smooth ride about 500 meters each way his back muscles were telling him where they were and that was as wobbly as mine if I needed a muscle relaxer. My husband walked on down and did keep a decent grip on the bench edge. Then let me know why they were wiping me out of the line up of shore excursions that their department for such things had assured me were no problem for a person who could not, even a little bit, walk or stand. All the places that were marked tender I had questions about and why I called rather than use their app. First with a regular adult size Quickie manual there was no way to get down the narrow downslope to the tender area and most tenders like Nome would either leave me in the RIB or my butt and chair seat soaked through getting the last few feet to solid beach. They straight out lied about inaccessible school buses in Alaska. We still hoofed it in Dutch Harbor to get pictures for my cousin as my Uncle has been on the Wichita up there before being called back to head to the Coral Sea. But St John, NB, Bar Harbor, ME and Newport RI have always been a tender for most ships. If you get a company like Holland America they brought the tender on the old New Amsterdam up over the davits about 3 decks higher than for the able bodied folks and once secure they swing the tender door open and I rolled over and a crew member helped my casters make a soft landing. Then we went down to the rest of those going ashore and loaded them. The reverse was the same with letting the majority of first then further up me, my husband and a women using a rolling walker. Silver Seas ships are, I believe, even older than Crystal's 2 ocean going ships. My husband did get a great pic for his abilities with anything digital of a polar bear on an small ice flow having his lunch of seal and the red blood against the blue white ice and the yellowish bear came out with sharp edges of contrast between each. As we left the Passage and headed to Greenland we had a decent display of the Northern Lights. But 2 days later for the last RIBs scheduled just to cruise the UNESCO site for most calving glacier coming off northeast Greenland just a few made it as close as our drone's, the Captain and the last icebreaker after ours thought safe. They turned the other groups back before they got to the walkway down and several in the first group were very happy they had worn the rental tall wet boots.
So, good pictures of the tender area including how you get there are needed. Be honest with yourself about your abilities but hey, we all have to go sometime. And have every measurement and weight anyone could possibly need in both American standard and Metric. Oh, and try the Silver Sweethearts idea and go to their blog or any where someone might be able to answer questions and may get you a pic of that area of the ship.