To have said something?

[SweetPotato17]

I was in the park with my 4YO DD and my DP today and there was 2 girls and a boy in there. The play area side said maximum age 8 years as it was just slides and swings and a play frame for young kids. The girls and boy looked around 13/14. At first they were swearing and shouting. Then I could see the girls whispering and all of a sudden one of them let out an ear piercing scream and they all were laughing. Then my DD was nearby and they did it again. Then the boy said ‘watch out, there’s a kid there, don’t fall on it, you’ll break its neck’ I’d had enough then. I said this is a small child’s park and told them to mind their language and stop being so immature. My DP said I shouldn’t have said anything and that I embarrassed us

Well done for speaking up. Your DP is weird.

YANBU, you were looking out for your DD and I think that's an odd thing for your DP to say. Were they there too but endured rude behaviour?

Well done …. I would definitely have said something!

Yeah I would call them out on swearing, but they are still children, and immature at that age

You were absolutely right.

No you did the right thing. Staying silent means you approve of their behaviour.
Your DP is probably feeling embarrassed that he didn’t say anything to them. Subconsciously his ‘male is the protector’ urge is pricking him and to deflect it he rubbishing your behaviour.