Seahorses are great! If you are looking to breed them (or at least attempt to raise the fry) then I do not recommend reidi or kuda. The fry are pelagic and really hard to raise!
Your setup sounds fine, just make sure there is not too much flow. And for the skimmer be sure no micro bubbles can escape into the main tank, they can wreck havoc on a male's pouch! I've run a seahorse tank for 3 years with no skimmer and no issues.
You might need more light for the seagrasses.
My setup:
33 gallon aquarium, rimless
96 watt PC light, hoping to put a 24" TEK light on there soon.
Small eheim canister filter
heater
tonga branchy live rock
several species of macro algae
mangroves (experimenting, hehe).
Mineral Mud substrate, with caribsea bahamas oolite on top
pair of H. barbouri
banded pipefish
I've kept H. reidi and H. taeniopteris (kuda) in the past. I am looking to add another pair, but not sure which species.
HTH
-Diana