No wonder, I would be too - that's totally out of order
I'd have made them leave last night instead of walking out myself - it's your house! Where did you go?
If I were you, when they come back I'd tell all of them that you're not there to be laughed at and it's not to happen again. And I'd tell DP - in front of the kids - that you don't expect him to encourage them to laugh at you
Shame you don't live closer, you could have come here for some peace and quiet