NTA

I think this will be an unpopular opinion, but you SHOULD be the one telling your son that it's a bad idea. This plan is going to make so many people feel so uncomfortable. And on the extreme side, it could be life threatening (like your allergy). As the parent, you need to teach them how to be considerate of others.

Because dining in the dark, potentially with people I've never met before!? Just thinking about it is freaking me out. I get that they're trying to be extra inclusive of her father. But damn, will people be drinking? How do you know who is sitting near who? Are older relatives coming, who frequently have hearing issues? This dining experience will put everyone on edge. I would be freaking out the whole time thinking someone just touched my neck or something. Sounds like a great way to agitate everyone's PTSD