In my wildest dreams I cannot imagine leaving behind some of my older ponies. Even those I got, as retired show ponies,, and bred for a few years, have a home forever with me. Sorry I am not being helpful. My girls stay with me where ever I might be. If I was going to move I would have thought about them at the time of the planned move. Sorry....JMHO
There certainly are places willing to do all that and would be great for it. My horse is across the country, but yes I did leave him in the care of someone I 100% trust and have known forever. I get a lot of pictures and he does great. There is another horse there that has been there a number of years and has an over seas mommy and my friend has taken GREAT care of her and the owner did not know her before. So there are places, the reason my horse is still there is the cost to ship and his age (24) and the lifestyle change it would be, hes currently out 16 hours a day on 5 acres with grass and hay 24/7. Arizona is nothing like that! Plus as a military family we would be looking at another move in his upper 20's back across the country (only two bases we can be assigned) so as much as it pains me, he stays and I know he has excellent care!
Take her! Get a good shipper that will put her in a box stall with a full load of racehorses going straight through to Santa Anita. She'll do awesome! I wouldn't trust my geriatric IR girls with anybody. Wish we could all go to California too (my home state). Much less toxic grass for the oldsters out there. Take her!
I just lost my 31-year-old. Even though he was healthy, I never would have considered shipping him any great distance. I remember the last year I showed him, how exhausted he was after a 4 hour trailer ride. You know your horse, but you would not be a bad person to decide to leave him boarded with the right person. I'm assuming you have horse friends in the area? Any friends with a little girl who would love to "help take care of" your pony at the new boarding place, groom him, send you pictures?
Considering her special needs, I would strongly consider taking her. If she is in good shape I don't see why she couldn't handle the trip with a professional mover. Done right, shipping doesn't HAVE to be that hard on the horse.
Some things to consider:
Is the pony used to being shipped?
How well does she hold her weight?
Does she get stressed easily?
What kind of turnout situation will she have once you move, and will the new place or the old place suit her needs better?
There are definitely retirement barns that will suit her needs. But giving up that control will be extremely hard.
Equine Express has a lay over facility in North Texas and they are very reputable.
I would ask my vet if they think the pony could handle a cross country trip and if so, contact Equine Express. Ask EE about the length of a lay over. They probably would work with you to extend the lay over if you wanted.
Just use a reputable shipper and get her a box stall. I highly recommend Equine express.
THIS!! Horses (ponies) are tougher than you think. A box stall on a good commercial shipper's van would not be that traumatic IMO. I would NOT leave her far behind and hope someone would care for her like I would!!!