John V - My suggestion would be to warm up with a couple of reef dives then go for teh Blue Hole trip. It would be sad to be so close and not do BH plus you get a chance to sample the outer attols.
Make sure when doing the reef your dive master takes you to the wreck. It is only a small barge but has a lot of fish life (large grouper & nurse sharks) plus a friendly 5' green moray in the bow of the boat. Make sure your dive masters takes some fish food.
Enjoy your stay.

TC