My very general take is similar to co counsel Mikes, but, of course, I have no knowledge about your states probate law and this advice is worth what I'm charging IE NOTHING. If I were asked your same question by a client in our state, I dont see any reason to open any full blown in Court probate estate PROVIDED you do a diligent search for creditors and send them Notice by Certified US Mail Return Receipt (Green Card) Requested and get them paid if the estate is solvent or if the amount owed is so small its not worth dealing with n just pay it.
I once handled a similar case where Grandma nor Mom ever probated any estate and mom still resided on property her Grandma owned so I had to open an estate BUT that concerned expensive real estate nottttttt a few cemetery plots.
Our state has an inexpensive procedure for settling small estates under $50,000 in which an interested person (like an heir) can simply file a small estate affidavit, insure all the bills are paid, file and pay any inheritance taxes, and thats all there is to it PIECE OF CAKE. If you can get all of grandma and moms heirs to sign off on, agree and be a party in that process and mutually deal with the cemetery plots thats how Id handle it here.
If the heirs cant agree on the cemetery plots AND THEIR VALUE IS WORTH WHAT A CONTESTED ESTATE COSTS, then that unfortunately may be what you have to do iffffffff its worth the expense???????
Id really really be talking to all concerned parties about the cemetery plots and seek an agreement,,,,,,,,look for and provide notice to and pay creditors (if estate is solvent),,,,,,,go the small estate affidavit route if your state has such
ORRRRRRRRRRR you can always do NOTHING (which in some cases Ive advised) n see if any creditors crawl out of the woodwork n wait n see what happens with the plots and/or worry about it later, LET THE CHIPS FALL
I HAVE TO ADVISE YOU TALK TO A LOCAL PROBATE ATTORNEY to at least get a preliminary and relatively inexpensive basic and general opinion and advice and then make your decision.
AS I ALWAYS HAVE TO ALSO SAY, CONSULT A LOCAL TRAINED COMPETENT PROFESSIONAL AND DONT HANG YOUR HAT ON ANY "OPINIONS" HERE REGARDLESS IF BY PROFESESIONALS OR LAY PERSONS