Our thought is that there is only a small percentage that would say Yes to this. Those people are probably only wearing a mask because you asked them to. These same people are most likely the ones (with families) who are traveling, eating out, visiting family/friends, playing sports, going to school - just putting themselves in the most situations and taking the most risk - with and without masks.
For these reasons, I think that If my kid was going to catch Covid, I think tots more likely of it being from someone who would also be attending this non- essential party is higher.