You’re very welcome, sir!
That’s very interesting that you have such a large shrimp population from the use of the intertidal mud, and your seahorses must be happy campers with lots of live shrimp to hunt and stalk between meals.
Yeah, I think transferring the seahorses to the 30-gallon refugium while you are away for a couple of weeks is an excellent idea. Your refugium sounds like my idea of seahorse Heaven and the ponies should thrive in their little personal patch of paradise, with all the live shrimp they can eat. That sounds like an ideal solution, sir.
I agree with you about the fish sitters — generally, the less you ask them to do, the better things will fare while you are away. Maybe just have your friend stop by once in a while while you are away to make sure all of your equipment is operating properly and to top off the tanks with freshwater as needed, and pretty much forbid him or her to do anything more, and you should be fine.
Best wishes with all your fishes, Kraut! It sounds like you have set up some outstanding aquarium systems, sir.