Adults only CLs how old is 'Adult'?

Hi

As our kids are growing up I'm starting to wonder if we can stay on Adult only CLs. (We only ever use CLs) the kids are 17 & 14 both quiet & responsible young people who've been brought up caravanning, taught how to behave etc. I've absolutely no worries that they'd be any trouble to anyone. 

I understand the idea behind adult only sites is to spare people from kids making noise & generally a quieter holiday experience?

Is there a hard & fast rule on this or is it simply down to the CL owners discretion ?

Any thoughts would be most welcome!

Gareth