Other options: stay overnight in Ft Lauderdale the take a shuttle to the port. Many cruisers use GO because they offer hotel pick up. Their website is http://www.floridalimo.com/
We have stayed at the Embassy Suites and Hyatt. Next week we are staying at the Hilton Grande Resort. You can also get a hotel thru Priceline bidding 4* only. That's how we got the Hyatt a couple years ago.
If you choose to stay in Miami, the Holiday Inn Bayside (http://www.hiportofmiami.com/
) is popular with the Bayside Market Place within walking distance.
Do you already have your flights booked? Why 2 different airports? I think that would be more expensive. I would rather fly out of FLL but depending on how late you flight is out of Miami, you might check out the hotel in the airport for a day use package. Their website is http://miahotel.miami-airport.com/
We tried to do this a few years ago but because we were booked the same dates as the Miami International Boat Show, everything was booked so we changed cruises. If you google the boat show for next year it says the dates are 2/12-16/2009. Hope this info helps. Enjoy!