I would give the company a call and investigate this a bit further. I wouldn't expect to get the fanciest cabin, have your choice of any sailing, or a seven day cruise. But it is worth a bit more investigation. The website does show that the cruises are 4 or 5 day cruises to Cozumel, Bahamas or Key West.
Once you found out what ship and date you would be sailing there is nothing stopping you from booking the rest of your group with another agent giving you the lowest price available.
This is if this company sounds legitimate and that you are paying no more than the activation fee and perhaps the $50 additional tax. Otherwise forget it. If they are going to hit you with port charges and additional charges it isn't worth it.