Good luck Kat.
As I said above, my father was a junkie, that's about as sick as it get's for him, us & my mother, but that still didn't relieve him of his responsibilities. JohnInKansas brings up an important point but it goes beyond what he points out. It permeates all of her present & future finiancial obligations & much of her future transactions, far more than just governement aid, it'll come into play when they apply for college loan applications & scholorhips, just one of many examples. She should know that she's doing & needs to continie to do what's best for the kids (the father is of no importance here, now or later) & their immediate as well as distant future too. As Susan also pointed out, it's the support for the kids' that's due them. Another part of reality is that if some one wants to do to what's best when it comes to taking care of the kids then they need to also take care & see to the needs of the mother or who ever the care giver happens to be.
It won't matter in the end if he fly's off, the kids will get by with or without him but it'll be his loss, later if that's what he chooses & if that's how he is he's not the decent role model the kids need to have around anyway & they need to see her actions as doing what's best for them too, they will later need to know that she acted properly on their behalf, she's a role model too. Good riddens to bad rubbish, that's his call & lousy choice not her's.

Barry