You teach someone else to feed them and get them to feed the ponies while you're gone. Keep in mind that ponies need to be fed at least twice a day, so you'll have to get someone to come in two or more times to feed them.
I have seahorses and I don't find them too hard to keep, but they are definately somewhat delicate. Seeing as how this is your first saltwater tank and your knowledge is still limited, I think the best idea is to start off with something easier to care for. You can set up the tank as a pony tank with all the plants you want and some live rock. Put something that will be keepable with seahorses later on, like a small goby or a firefish. After a few months of keeping the fish, extensive research of seahorses, and when you feel prepared, you could probably care for one. Seahorses are usually not for the beginner or average keeper, which is why I'm recommending you get experience with something that is a little less delicate first.
Just a warning about male seahoses: the male seahorses can some times get air bubbles trapped in their pouch. In such an event, the seahorse will start floating around the tank and won't have control of his movements. Should this happen, you'll have to open up his pouch yourself and release the air bubbles. This is usually referred to as burping the seahorse.
Let me also say that seahorses do not need too much room. They are not too active and usually just like to sit around on a plant for a while. A pair of Kuda seahorses can easily be kept in a tank as small as 20 gallons. You don't need to go as high as 50 gallons as metalac said you do.
