There are some questions that need to be answered in regard to this situation.  Since he died without a Last Will and Testament in place, was his estate probated?  Is this in a community property State?  Was the property held in a trust or other means (i.e. what manner of vesting did they own the house in)?  Was the probate order recorded in the Official Records?  Was a final order of distribution issued in the probate, if probated?  Do the children hold any other claim to title (co-owners, beneficiaries, a new / undocumented last will)?

 It's not like a quitclaim deed for such spouses would hurt if they are willing to execute them, but I'm not clear as to necessity based on so many unknowns.