We had a 4 day WDW land vacation/3 day Bahamas cruise for our honeymoon back in 1993 which we booked through the travel department at Filene's Basement. It was on Carnival Cruise Line. You don't say whether you want a cruise or not, but that's been my only experience with the Bahamas. It was a nice cruise, but we like the WDW portion of the trip better.
There are some nice, short cruises to the Bahamas out of Port Canaveral, not too far from Orlando. Disney Cruise Line and Carnival both offer them and another line as well, although I can't remember which off the top of my head.
Real Florida Excursions offer an excellent 2-day trip to the Bahamas, taking a coach down to Miami, having some shopping time in Miami and then flying to Nassau for an overnight stay. You return by cruise ship the following afternoon, with all the food you can eat (!), and come in at Port Canaveral. All for around £250 per person. Look them up on www.werusa.com. You can also look into another good excursion company, International Divers, who were looking at doing a similar tour the last I heard. They can be found at www.swimdolphins.com
We did this for our honeymoon. We booked it ourselves. check us air and delta to see what islands of the bahamas they fly to. Be prepared to fly in a small plane and pay 250- 300 dollars pp