A difficult thing to approach since as you say assisting the child now can mean trouble for it down the line, I do think with the friends and their children a person can bring it up quite easily example

Random comment from you:

" You know what I don't understand? These parents that [insert thing they do that is retarded] "

They reply :

"Oh but I do that"
discussion has been opened

"Oh really you do? Well... Blah blah blah"

or they shut up and maybe you see they change their approach.