How to Tactfully Tell Other Parents What They’re Doing Wrong

Hi Nicholeen,
I've got a question that I haven't seen answered anywhere (not even your podcast/YT channel, which I love).
My kids are fairly well behaved. We've put a lot in practice what you teach (disagreeing appropriately, etc), so they're even better now, but they weren't too bad before that.
I'm having a family over for a week who has 2 kids. Their kids are disastrous at times (screaming, spitting, breaking other children's toys, etc.), and although the parents are aware of this, and I know what they're doing wrong, I don't think simply telling them what they're doing wrong is really my place, nor would it be well accepted.
How would you go about opening the subject, and what would you explain? I feel there are so many skills (parenting and personal) they'd need to learn that I wouldn't really know where to start…
Thanks for all you do!