Would that be so bad? If this is what your life is going to be if you marry this person, and it’s doing this to you, and you are too anxious to do what’s needed for your health, it doesn’t sound like it’s a good idea to marry this person. This is what your life is going to be like every year if you feel obligated to attend optimal masses that hurt you—and to be sure, this sensory overload is legit. I attended the Easter vigil & slept soo much and was good for nothing the next day, even today I feel wiped. You can ask that your fiancé be the one to tell your future in-laws, but if you can’t self advocate in this small situation, it’s a sign that maybe you shouldn’t be with this person if you can’t be open or honest without extreme anxiety. I’m not saying anything else about the relationship but this kind of basic thing is a huge red flag. It could be that there would be no problem at all if you could pluck up the courage to self advocate, but if you think they’d be offended, that’s horrible and would be a sign that they’re ableist. Take care of yourself either way.