ok, nothing here private or anything so just posting instead of IM'ing. Talked to my CPA who I love like my own mother. Their advice is as follows:
1) never call the IRS for anything no matter what. they not only don't know what they are doing but they will waste your time pretending like they do and make stuff worse.
2) if you have their name, address, and SSN there is some form you can file to get that extension but I'm guessing you don't have that SSN
3) are you confident they even needed to file taxes? sounds like maybe they weren't scrooge mcduck. may not have to do anything.
4) if you believe they would have had to file and don't have the info required just do nothing right now. you can file it late but the penalty will be minimal and you should document that they are deceased and the situation when doing so and could get a pass.