Well, I've read a lot of historical novels (both written in period and written later) and a common trope in pre-20th-century works is kids being too young to go to the party and they want to do so badly. And I know enough about the history to know that that "kids don't go to formal events" never went away among the wealthy the way it did in other classes, partly because middle class people stopped doing formal events except for weddings and stuff like that. But even up through the 1960s, when middle class people threw a party, the kids usually didn't attend, they stayed in their bedrooms. Kids going to parties with their parents is a fairly modern thing, actually, unless we're talking things like church picnics that are explicitly designed as family-friendly events. The whole "children should be seen and not heard" was powerful and ubiquitous and guided child participation in social events, and CONTINUES in rich families to this day.

And it totally is a work event, and the work is Rich Person Socializing And Being Seen, and also Rich People Networking to arrange things like business mergers and marriages between The Right Sort Of People.