@jemsm
You are in a difficult stage and seem to be handling it well. You are asking for some guideposts to help balance hisright to privacy vs. the need to have others understand new behaviors. I will share what I did and what drove that.

1. We did not ever have a discussion in which he asked me to not tell anyone. In part that is because we have rarely spoken about his condition. We have operated so that he does not feel like things are changing. I adjust what we do and how things get done so that he maintains his sense of wholeness as his capabilities decline.

2. I told a few people early on because I needed to be able to talk to someone about what was going on. Get ready, though. People will react in various ways and not all of them will be helpful. For example some friends kept saying things like "Oh everyone our age forgets a few things now and then!" I'm sure that they were trying to make me feel better but instead it made me feel like they were saying I was making it up, when I was trying to say "This is happening!", but saying it gently.

3. Over time I told more people as needed --privately and confidentially -- with the stated intent of making him comfortable as changes occurred and enabling people to feel comfortable with the changes too. At this stage I told a larger set of friends, and all of our families. (Consider this: Do you really need the added burden of keeping track of who knows and who does not?) In your case, yes, this would be going against his wishes. In our case, I have consistently acted based on what would be make his life happy, not what he might say he wants.

4. To help people who do not have experience dealing with someone with dementia, look up the very concise and helpful resources on Compassionate Communication from the Alzheimer's Association. e.g., https://www.sdalzheimersproject.org/content/dam/alzheimers/en/pdf/Compassionate%20Communication%20with%20the%20Memory%20Impaired_Alz%20Assoc.pdf

All the best,
Keep posting. We all benefit from the exchanges.