4 is going to be a crowd on all but the largest skiffs. The majority of the guides out of B&M's are going to have 17' or 18' skiffs and probably won't want to take 3 guys on their skiff. If you're looking to fish one day and bum around a couple more, maybe run down to Padre Island and book a redfish guide in Port Isabel or Padre Island? The area mostly has a sand bottom, and you can find a guide that will get you guys out of the boat and wade to tailing reds. It's a good intro to saltwater fly fishing, and reds aren't that finicky when it comes to eating a fly in their general area.
Also, August is a terrible month to fish the keys. Permit fishing can be good, but not many bonefish around and the tarpon have mostly migrated through and taken a lot of guides with them. Making your first saltwater fly fishing trip a permit fishing trip is like deciding you want to try golf and buying clubs a Dick's on the way to a US Open Qualifier.
or do this