Before I begin, I do realize that there is another form that can be used, SF 180 or something like that. Anyway, I realized that I don’t know much about what my grandfather did in WWII (though we did talk a little about it and Mom was able to tell me some, so it’s not like I’m completely in the dark here.) Anyway, the easy-to-use online request form (eVetRecs) is meant for use by either a living veteran or by next-of-kin. The dropdown specifies the following categories: surviving spouse that has not remarried, father, mother, son, daughter, sister, or brother. To me, that means I could theoretically get the records of my mother after she dies (which hopefully won’t be for a long time) as I would then be the son of a deceased veteran, but I could not get my grandfather’s records now as I am a grandson, not a son. As I said, I realize that if I really wanted to, I could use the standard form 180 to probably get the records. Anyway, I guess the question is what does the NARA mean when they limit the use of eVetRecs to only the abovementioned categories? If, for example, in the future when my grandfather would have no living next-of-kin as defined above, does that mean that the only way to obtain those records would be through SF 180 or would somewhere in the direct line of descent be enough?
When I did this for other genealogical records from INS and the National Archives, the records needed to be older than a certain age (100 years IIRC), or I needed to have permission from the next of kin. Some of the records were old enough that they were public domain, but some weren’t – as they pertained to my grandmother’s parents, I simply drafted a 2-sentence release for her signature, stating that she was the closest living next of kin, and that she authorized the relevant agency to release the records to me. So you probably just need the written authorization of your mother.
However, if the rest of my experience holds true, the V.A. will want you to fill out their in-house form anyway. I recommend calling them (if you can) and finding out who their Freedom of Information Act Officer is, or alternately (if you’re not in a big hurry or don’t want to spend endless hours on hold with large Federal bureaucracies), writing a letter to the FOIA Officer.
Also, be prepared to wait quite a while for them to get around to making the copies for you (possibly several months). If you have time, and you’re near a NARA branch, you can usually go in and do research in the archives yourself.
It’s been several years since I’ve used a SF 180, but at that time they had the same next of kin provisions. I simply ignored it and neither Ken Starr nor John Ashcroft knocked on my door.
AFAIK, anybody can obtain anybody’s service records except for the medical part thru a Freedom of Information request anyway and no one except the veteran can obtain the medical portion.
The real problem is a large portion of these records burned up in the early 70s. Secondarily, the kind of info you must include in the request is usually the very stuff you are making the request to find out.
I am not telling you to just click the son/daughter choice. Remember I am not telling you to click the son/daughter choice. Remember I am not . . 
I don’t think I’d be doing this any time soon. I was mainly just curious.