Last time we sailed out of Miami, it was just my hubby & I. We were going for a 4 day cruise so we thought that we would splurge on the hotel, and really make it seem like we were gone longer....we chose the fantastic Mandarin Oriental. Man oh man. It was the best. I wish it wasn't so expensive. But in our situation at that time it was great. There were 4 poster beds on their private beach, the view was great, the food, the drinks, the room was unbelievable. So if you can afford to add that much on to your cruise, this is the place! I am now currently looking to add a pre-cruise hotel in Miami for March for my hubby, son and myself. Unless the Mandarin Oriental should slash prices, we won't be staying there this time, but I'll be looking at it when we sail away!
Good Luck hotel shopping, and I'll be watching to see what others post.