So he was in the US Army or US Army Air Corps or early USAF? Those are the only records stored at the NARA at he time and were burned and only about 80%. If was any other service they should be available at NARA. Does he have a common name? Do you have his service number? Did he use GI benefits for college?
The information required to be known by cemetery is the status of which he left the Service. Honorable, General, Dishonorable etc.. When my step son passed away, the National Cemetery in NY only wanted a copy of is Honorable Discharge Certificate, not his DD214 of is US Navy Service during Vietnam. Our grandson couldn't find his dad's copy so we faxed a copy, given to his dad when his son returned home.
My condolences for your loss but at that emotional time are you sure they need what you think they asked for? Does another family member have posseion of your grandparents keepsakes? Might they have a copy if your father's Discharge Certificate? My husband's and his son's looks like a diploma or degree certificate as schools issue. ok couse the DD214 also stats the discharge status, but the certificate should work. contact your local Veterans Affairs Office.
NARA ADD online databases have US Army (including Air Corp) WWII Enlistments 1939 - 1947. That database includes Army Serial Number.
Ancestry has it too but no serial numbers. They do have Navy and Marine muster rolls with serial numbers.