I know it can be stressful. I did it for my mother's will and there were stressors even though she kept it as simple as possible. But as a wife, I would still expect to be executor or one of the executors of my DH's will. That's just how I''ve always known it to be. And if he first had me as exec and then changed it, I think I would be offended. Ok, maybe I would be partly relieved, but also a little offended. Maybe it's petty, but I would feel as if he chose someone else (his DS in this case) over me, as if he trusted DS more than me. I wouldn't mind his choosing both of us, but just DS? I am very sure that would bother me, especially if it were a change from before, as in the OP's case. And, to me, it makes it more suspicious as to how this new will came about.
But, TBF, onneker, it's possible that DH was just trying to make things easier on you. In fact, maybe you should do the same for him, especially since, sad to say, he might easily not be here to execute your will, anyway. Most important, tho, as far as your will is concerned, IMO, is to change your beneficiaries and be prepared to sell the house if you need to.
I trust none of this will color the love and care you give to DH in his illness. Love, after all, is more important than all of this.
Wishing you peace...