You mention resale value, so maybe this doesn't matter.

We've been thinking of doing some remodeling - but my wife in convinced she's never leaving this house. So for us, I'm thinking we need to keep a tub of some sort for when one of us gets too old to stand in a slippery shower.

We're used to 1 sink, and I can think of very few times that having an additional sink would've been a big deal. I would probably stick with the single sink, knowing it may inconvenience me by a few seconds now and then when I want it and my wife is using it. If there is plenty of counter and mirror space, that will be super rare.