This is one area of child support I am not familiar with- however I am familiar with *some* estate law....it is my understanding that any outstanding (legal) debts must be paid before any funds are dispersed to family members etc. I also know that you have to sometimes file this with the estate....if he had someone set up to manage these affairs then you need to speak with this person. If it is an outside source such as an estate lawyer/bank etc, then you should be fine as they have to obey the confines of the law. This should be the same with an estate manager who is a family member...but many times inappropriate and inexperienced people are appointed to such positions and will not bother with things they don't want to, such as you...even if they are obligated to by law. I would have your wife speak with the designated estate manager, or power of attorney of the estate and have her gage the situation. If she feels they are going to gyp her, I would most certainly seek the advice of an estate/probate attorney- the consultations are generally free or a small fee. Then you should know where to go from there.
Definitely pursue it, this IS something that should be paid from the estate. Also speak with the authority who was pursuing the support...especially if it was the Office of the Attorney General, as a government agency they would be able to help you a great deal, as well as free of charge, for recovering those funds.
And to those who say let them grieve- yes of course a family needs to grieve. But business must also continue. There would be no funeral, flowers or burial if everyone just sat around crying...things have to get done and unfortunately this is one of them. They wouldn't have to be "bothered" with it if he had done his fatherly duty in the first place.