I called a few local vets (we don't have many), including my own regular veterinarian, but they only make house calls. The nearest clinic is over 3 hours away.
I talked to a friend who mentioned donating their carcass to the zoo. There is a local big cat sanctuary that I have called about making a donation. I'm waiting for a call back from them. I could ask my brother, who is an experienced hunter, to go with me to haul the horses there alive and we may be able to do gunshot euthanasia on site and have the carcasses fed to the large cats. I don't know what my brother's response will be as we grew up with these guys. They've been a part of our family for a long time but I can't stand to see them be allowed to starve because of my father's stubbornness.
This sounds like the best option. If your brother can't shoot them( even a hunter doesn't like killing family pets) they will do it there. Give your dad a break here. He may seem irrational here but with age sometimes things are really hard to handle. These horses have lived a long and full life and shouldn't be passed on to someone else to become their problem. Hope this works out.
I haven't read all the responses so I'm not sure if someone has mentioned this, but what about your local Animal Control? Our AC was out about a week ago and picked up two horses. They will eventually be up for adoption if they aren't put down....they're about 10-12, never handled, so I'm not sure what they'll end up doing with them. But, your local animal control might be an option.
With the younger of the two having pretty significant arthritis, I'm trying to avoid this at all costs as I feel it would stress a lot. If I can't find another suitable option, I'll have to consider it strongly.
Yes, that would be difficult, but 3 hour drive is a lot less stress than starving to death. Better to do it before they go hungry.
This may have been mentioned. If I missed it, I'm sorry....
Where I grew up we had a man who shot horses and livestock. That was his job. You could easily write a book about the town I grew up in, and he would be one of the central characters. Anyway, while it seems like a terrible death, if you can find someone who knows how to do it, it really isn't bad at all. The horses who meet Moses (that's his name, and I swear he is 200 years old but never shows a day of it) stand in their field, eating grain, and then they are dead. There is hardly any blood and they just drop, dead. I can't remember what he charged, but it was a fraction of the cost of any other form of euthanasia.
I know this is only one piece of the puzzle, but I thought it was worth adding. It might be worth asking around if there is someone who does this work. If there is, chances are they could help you with the other aspects of your problem as well.