ashe. LAUREL came with Steve because she's not missing out on her boyfriend's grill skills. She's very pointedly not drinking, but she's chill about other people doing it. She'll be social.
CLAIRE came because Jody asked and dragged Kaia along. She's never been super into the whole...socializing thing. But there's alcohol and food. So she'll make an effort.
SCOTT is all for this kind of thing. He'll be radiating dad energy, because heck yeah, cookout. He's happy to get to hang out with Hope and do normal things and meet new people. Plus, he can make sure ants don't cause problems. This is a situation where Ant-Man is the perfect superhero.