Best beach (and only) is at Paya Bay or Fantasy Island. FI also has a pool but their dive op doesn't measure up to Anthony's Key or CoCoView. CCV is isolated by being on its own seperate island- you can rent secluded beach houses there, and AKR is nearer to thw West End where you can party at a different bar each night. CCV has the only shore dive and the dive op is world standard along with the boats. AKR has a dolphin pen and slightly fancier dining that you have to cliumb 68 steps to enjoy. yes AKR can be quite busy, not only with day tourists, but because the main path thru it is the only road to a secluded village- so everybody comes marching thru.
FIBR has the fanciest dining, such as it is, but quality and service is unpredictable, The dive op is trying real hard, but pinched for $. I believe they also have tennis and some terrestrial sports of that ilk.
Paya Bay has a nice beach and a great view- nothing more.
On West End there are several operations that you could get an ala carte package and have a little for everybody (but not a lot for everybody).
Roatan doesn't look like it will fit many of your expectations, sad (?) to say, there isn't much to do besides SCUBA and drink beer.
There is a rain forest canopy tour slide-for-life thingie, and iguana farm and natural gardens and water taxi tours. If you tried real hard you could get all that plus the horse riding in by two days.
Lting on the beach? Well, only at the two places I mentioned, FIBR you can kind of get away with topless, and anywhere you'll be needing bug spray, the no-see-ums.
August can be rainy. I was there for two weeks and it rained for one day- go figure. Allergy season? I would imagine it runs all year long depending on what you're alergic to. If you're talking sealice- take benadryl or if you're really reactive, epiject. On the South side (FIBR & CCV) we didn't need a/c, the fanms were fine, at least at CCV. I'm sure on the North side it got pretty moist.
If you want the best shore dive environment, perfectly suited to OW dives for certification, I can only recommend CCV. Their front yard is literaly a swimming pool amid the ocean. Their rental gear at DockSide Dive Center is always in great shape and will be just going through it's 18 month replacement cycle by Christmas this year. Always nice staff at dive shop. No other resort has a real shore dive that comes close.
Getting married and doing students open water dives. Is your name Martha Stewart?
I absolutely guarantee you'll see whale sharks. So that ought to be okay, right? Just tip the DM. (I've seen 'em on shore dives from CoCoView, but you never know!)
RoatanMan