To meat or meet?

What would or should you do?
You are one of a bunch of madrichim/counsellors at an American style summer camp for young primary age kids, many of whom have limited exposure to Judaism.
To show their gratitude and hospitality, the parents of one child, who keep a kosher home, invited the counsellors to dinner, during the nine days.
Unfortunately, they didn’t consider the need for milchigs, and a nice meat meal was served.

Do you politely decline, and all claim to be vegetarians?
Can attending a Siyum after the event help?
Should you consider that embarrassing the hostess is worse than keeping one part of Minhag Aveylus?
I’m aware that there are leniencies when one encounters royalty and the like during the nine days; does this count?

I hear some of you quoting the “fifth” chelek of Shulchan Aruch which encourages you to be a mensch at all times.

I haven’t looked into this. Any insights?