“(in general, it’s no big deal to say something is assur, but it takes a real rabbi to find a heter.)”
You just posted exactly what my former Rov Z”TL used to say whenever I asked him to pasken a shailah and he gave me a heter that I never in a million years expected to hear. he would say that any rov could say it’s assur, but it takes a real knowledge of Torah to say it’s muttar.
I hope both you and your parents live long and healthy lives. And no, parents should not outlive their children under most circumstances. It is not the natural order of things. So both kids AND their parents have to take care of their bodies, minds, and neshamas.