If you have insurance cards for them then he's done what he has to do. Don't worry about the stability of thier marriage, she can't delete people from coverage if she gets angry at him... it has to be during the election period or it has to be a "qualifying event" such as death of a beneficiary, divorce or marriage, before she can change her coverage. and in that time, he would be allowed to get himself & them covered under his own eligibility with that employer, or if he's no longer employed by that employer, he'd be offered COBRA. It's his own stupid decision to go that route if his marriage really is rocky, so the costs of his buying insurance for his kids through COBRA would be his own stupid fault.

IF that happened that they separated, then you'd have to deal with making certain he kept them covered, because COBRA would not be sending teh notices to you... but that's not an issue at this point, so leave sleeping dogs lie. Truly, it might be cheaper for her to cover them, depending on how their employer handles the insurance issues... and as long as it's the smae as he'd have gotten, who cares if he took it or declined it?