I would recomend doing it on your own because the cruise line charges around $65 an hour, but your only in the air for about 5 minute. You can usually find it on your own for the same price but you're acually in the for 30 minutes to an hour.
I did it in St. Thomas last year near Coki beach. It was around $60 and I was up for 15 minutes. It was awesome! I suggest doing a google search for parasailing at the ports you will be at.