bakerjw

Not to derail a thread.
My wife has been visually impaired her entire life too. She can see well enough to have been able to ride her bike to and from where she used to work though. That said, her balance is not all that great but some of that comes from poor upper body strength.

To the OP. As some have mentioned, a lot of it is a trust issue where tandems are concerned. My wife used to freak out if we broke 30 miles an hour on a descent until she got used to it and trusted my judgement. Myself, I don't particularly like getting over 40.
Then we took out mountain tandem out on the gravel. It was the same thing all over again but this time, there was noise of gravel crunching and getting spit out as we descended. I also have to move the bike around a lot more to avoid obstructions.
Early on, when we would take our road tandem out, I would lean us into curves. Once or twice when the bike was leaning, she fought me and tried to keep the bike upright. I gave her a little reprimand because I had to get heavy on the brakes to keep from pushing off the side of the road.

Again, as some have mentioned. Try a rental or see if anyone in the area has one to try. There is a joke in the world of tandems. "Whichever way your relationship is heading, a tandem will get you there faster." We say it jokingly but it is true. Luckily, my wife loves our tandem rides. Usually more than I do, but then again, the stoker is the one who puts out all of the power.