++++1 on the nitrox for your OW diver. That diver should be able to do these dives, but without nitrox they will be missing out on a lot of bottom time.
Be aware that almost everything in this area is drift diving and currents can be strong. That is absolutely no problem for the reefs, as you just descend and drift along. The wrecks are also done by drifting in to them and drifting away from them when you are ascending. Those dives mean more discipline on the descent (in the water and down quickly with no fiddling around on the surface) and maybe the ability to follow a compass bearing to hit the target once you are down. It also means (for all dives) holding your safety stop while drifting and without a visual reference or line to hold on to, unless you deploy your smb at the stop. A good OW diver can do all of these dives, but I just wanted to let you know.
Be aware that almost everything in this area is drift diving and currents can be strong. That is absolutely no problem for the reefs, as you just descend and drift along. The wrecks are also done by drifting in to them and drifting away from them when you are ascending. Those dives mean more discipline on the descent (in the water and down quickly with no fiddling around on the surface) and maybe the ability to follow a compass bearing to hit the target once you are down. It also means (for all dives) holding your safety stop while drifting and without a visual reference or line to hold on to, unless you deploy your smb at the stop. A good OW diver can do all of these dives, but I just wanted to let you know.