If any "friend" is stopping him from feeding his son, that's a bad friend! If I had a new bloke (as a friend or boyf, or even a new girlfriend for that matter) who had children coming over, I'd make sure the children were well fed - but I'd still expect him (or her) to make sure the children were eating. If your XH and his friend aren't bothered about feeding your children, I'd call him up to say he was dobbed in... that he can't be bothered to feed his children when he's playing with his friends! Don't say "female friend", just "friends" in the abstract so he knows you're more concerned about his level of parenting (and his new friend's level of parenting) rather than if he's dating or not.