Fixing up the barn! Ideas wanted!

Well, I've saved up a little extra cash and now I'm ready to get some more work done on my "barn". We started our barn and made it functional about a year ago. It has two stalls with dirt floors, tack room with wood floor. (One stall on either side of tack room) and it has a fairly large overhang/walkway with sand\dirt where I have crossties. In the future, I want to add 2 extra stalls on one side and a little "storage stall" on the other. But for now I'm focusing on the the little stuff. My husband dredged our pond and got about 4000 yards of dirt/sludge. It compacts really well. He is leveling out the pasture, around the barn, and leveling out an area for another paddock/grass riding area. Well we live in Florida and before my husband leveled everything our property was almost 100% sand. This sand is driving me insane!!!! It gets everywhere, it's impossible to keep the horses feet cleaned, etc. So now this dirt is much more compacted, and nicer. But it is still a pain. We need grass!

Okay sorry for the rant but now for ideas, I am thinking about putting stall mats down over the compacted hard dirt for our walkway but I'm not sure what to put on the outer side to prevent the dirt and sand from the outside coming in constantly. My husband was thinking railroad ties but I'm looking for some other ideas as well.

Second, I want to close up the stalls a little more. The man who built are barn built is with extremely tall ceilings and rain, sun, etc gets in more then I like it too. The roof goes in a slant. We used 2x4x12s (I think) for the stall boards, but they only board up to about 8 feet. I want to board up the top open half but would plywood be okay for that? Or would you recommend any other type of wood?

Third, we are making a wash rack (10x10). We were thinking to put paver base down, then lay pavers, put mats over it, and sort of fence it with two rails on each side and one open side. Most ideas I found online said to use concrete for wash racks, but that would be to expensive. We have a ton of pavers left over from our patio so we thought it would be a good idea.

Also - now that we are completely surrounded by dirt we really want to get grass growing. Now I am planning on allowing my horses to graze once we have grass, but I'm still going to feed hay and grain for nutrition requirements. But I'm hoping by having grass I can at least cut out the "filler hay" I feed them now throughout the day in slow feeders. What kind of grass is best for Florida? How many months until it is okay to graze? How often should you rotate pasture? Would you do sod or seed? . (I've never had to manage my own pastures before!)

Thank you so much for whoever reads all that there is so much more to be done but of course I have to present it to my husband slowly so he doesn't have a heart attack!

Any ideas, pictures etc for barn renovation is wanted! Please share what you do or done in the past.