Ok, you're completely not understanding this situation. They're old. They need help. Period. The only question is how they get the help they need, and the price. There is always a price.
Also understand they're not being frugal. They're being cheap. Frugal is not spending unnecessarily, and getting a good price on things you need. Cheap is not getting things you need. They need assistance. They're not getting it. That's cheap.
There are 4 basic paths this can go.
1. They move closer to family who can and will assist them.
2. You move closer to them.
3. They recognize that they need assistance and start paying for it.
4. No one moves, they don't get assistance.
Is #2 an option? Yes? Do it. No? Don't even mention it. It's not selfish to decline to uproot your life.
4 isn't an option. It'll result in illnesses, injuries, etc that will cost a bunch of extra money and that's assuming they survive whatever the original issue is. That's pennywise and pound foolish.
If you're not moving, you need to talk to them. Possibly as a nice big family, get everyone together. Discuss options with them. Since they want to leave money for the grandkids, you're going to need to pull the argument that the grandkids do not deserve a lifetime of guilt because their grandparents suffered in order to provide them with (presumably) unneeded money. Money is just money, and your parents are hurting themselves rather than spend it when they need it. Yes, reverse guilt trip them. The solutions are they they move, or they start spending some money for the help they need. The alternative is property damage/decay, unnecessary illnesses/injuries followed by medical costs, reduced quality of life, etc.
Also start helping them take advantage of any services/discounts they're eligible for. That will sooth the cheap side of their emotions.
If getting a social worker or some person who works with elderly people is an option, do it. Because they're used to dealing with people who need help and refuse to admit it, or pay for it, or whatever.