It would for me. Due to her age and that you've only had her for a couple of days, I'd be focusing on bonding with you rather than meeting a bunch of new people and some dogs. And if she is a bit timid you really want to be especially careful not to toss too much at her too quickly and overwhelm her. With the right kind of socialization her demeanor should be relaxed and happy. If she's at all stressed you're doing more harm than good.
I think you're right, I think I'll just leave her at home with my in-laws while we're at the party. Maybe next time we visit without all the people there would be a better time to introduce them together. We don't see my family that often, and I know he's not the kind to take his dog to puppy classes and walk him around to meet and play with other dogs.