Well, we are in the same boat. We'll be taking our 2 year old on a cruise with family soon too. I haven't done this yet, but I figure it can't be too much different than staying at a motel for an extended period of time. We generally have had to leave the room for my daughter to get to sleep or take a nap. We've taken her monitor and just went down the hall to a sitting area OR gone into the bathroom until she falls asleep and then reentered the room quietly to sit and read while she slept. Just take a lot of quiet entertainment for you! Make sure you have some of your son's favorite toys, blanket, etc for sleeping and playtime. Take more than you think you'll need of everything because finding stores with familiar brands is difficult in many ports (we have cruised w/o child before!). Don't forget toddler snacks (fish, cheerios, etc) because they probably won't have that on the ship. Snag an extra fruit from the buffet for later too! Don't forget the swim diapers and baby suncreen since many families spend hours swimming on the deck. A hat is a good idea too. Dress in layers since the decks can get cold (constant breeze due to ship moving). Hope that helps.