I don't think the first party is usually insanely busy. I think the concern is about it beign Friday night of a 3 day federal holiday weekend. If it's the only party you can go to, I'd do it. If you can stay for the 2nd party, I'd choose that one. Although if that's Sunday, that will still be in the 3 day weekend, so not sure how that will be. But generally Sundays are far better than Fridays.