AITAH for not wanting to go to a family party where there's strangers attending?

I'm 22 (F) and my sister-in-law invited me to their home where she and my brother are hosting a 4th of July party where their kids and a few other in-laws will be there, all of whom I'm comfortable with because I've known them for years. But BOTH my sisters-in-law mentioned inviting a few of their own friends over who might also bring their kids as well. I have really bad social anxiety and don't feel comfortable around strangers, and it's already a rather small home so it will feel a bit cramped with so many people over. I don't want to attend the party just to hide upstairs where there's more room (living room and dining room are barely going to have enough space to sit everyone...) so I'm thinking of just staying home. AITAH for being anxious and not wanting to go? I've never met the people they plan on bringing and that doesn't help either.