If I remember correctly what I've read from other posters. If you turn in your clothes on the first day, you should get them back the next day. Don't count on having them for that evening. I know there's a charge unless your in a suite.
If you just want to get a few wrinkles out, there is a laundry room with an iron on each deck for you to use. I went to the laundry room the first day in the early afternoon and spent 15 min ironing out everything I needed for the rest of the trip. It was quick and easy. Oh yeah.. and it's free.