My only point would be that, whether you care or not, once you've gone, they are likely to wonder what they did wrong.
The act of not telling them is not neutral, it is still an active decision, and if you choose not to tell them, most people would think they had failed you.
Your dignity is important, but I wonder why you think that them knowing, and being sad/alarmed/ wanting to support you, is undignified?
Depending on how long you have to think about it, I wonder if there is room to tell them, but be very clear they should not try and"rescue" you, or come over as often as possible.
If you feel they can observe your own plan or rules, you may have a better few weeks, months, with opportunities to connect with them. That doesn't mean they need to be around for the end, or involved in your care.
You would not be unreasonable to keep it secret, if you truly think you would prefer it, but, given you've asked the question, I'd be interested to know what you think might happen if you let them in, and what you would have to deal with.
I'm very sorry, it's a hard situation.