Like Neaxan said, fill out the Guest Special Need Form ahead of time and it will be waiting for you in your stateroom.
If you're already on board, simply request it from your stateroom attendant and he/she will have it waiting for you in the evening when they perform the evening stateroom service. (The time when your towel animals and cruise compass appear)
In January, a flight schedule change made us need to get from the Baltimore port to the Reagan airport in DC. We simply did a one-way car rental about a mile from the port (Hertz) and chose for the Reagan airport to be our drop off location. It actually ended up being less than other forms of transport.
This can give you the freedom to go where you want, have a place for your bags, and get you to the airport when you need to!