I am only really familiar with the large horse world with this regard but I can tell you that here, in WA state, you almost can't give away a horse. I did rescue for many years and ate the costs incurred when I was lucky enough to find a good home. I have a solid contract that I use, written by an attorney, and I keep track of every horse I've placed. I finally quit when my own physical limitations required and am now just playing with my minis.
If these people are A+ people, you feel confident that they are knowledgeable and financially able to care for him, then put him in a lease contract and if anything, have them give you a deposit that goes toward his purchase price. If they don't keep him, you can opt to refund it. If anything happens to him, you have some insurance.
In my way of thinking, knowing that my horse was going to a really good home is worth it's weight in gold. It is a pain and it's expensive but doing your homework on them (check references, do a sight check, etc.) can make your heart feel better about the whole thing.