That sounds good. Prep, ceremony, formals, reception. So 4 or 4.5 hours should be all you need. The lucky thing is that you have a set time where you HAVE to be back on the ship, so it's not going to run over and you won't have to negotiate for more time. But many times the reason why things run late is due to the salon, make sure you have plenty of time and probably at least 30-45 minutes more than you think for the salon/makeup. Also that they know you have a strict timeline to get back onto the boat. Otherwise it may be almost 11 by the time you get finished and all the photographers time is gone. Good luck and happy planning.