We were recently on the Dream and had to deal with our youngest son's type 1 diabetes. In some ways it was a similar dilemma, but obviously very different in other ways. He drinks a Boost glucose control every day for breakfast and sometimes at night to keep his blood sugar from going low. We brought them on the ship with us. My first recommendation is to adjust your expectations for the time you are on the cruise. We knew that strict control wasn't going to be an option. Our goals for his blood sugars on the cruise were very different from our day to day goals. That's just the way it has to be. Otherwise none of us would have had a good time. Do your best to get your son to understand that changes made to enjoy the cruise are temporary and won't continue when back home. Second recommendation is to bring a mix of bottles of Boost (or preferred supplement) and the powder. You are correct that the powder isn't as calorie rich as the bottles, but this is a situation where you have to do the best you can. Bring enough of the bottles for 1-2/day and enough powder for another 1-2/day. The last thing I'd recommend is exploring the websites that show all the different food options available. There are websites that show the current menus for the non-buffet dining options. Review them with your son to find the things that he would be excited about eating. Try to learn which hours the different options are available. I'd especially recommend reviewing the room service menu. It is available 24 hours/day and included with your cruise price ("free"). My son's favorite thing was the chicken fingers and french fries. His favorite thing about the whole cruise was on demand Disney movies and room service. That's the way it goes sometimes. Ultimately just do what you can to not stress over a few hundred calories here and there in what is a temporary vacation situation. Remember it is a vacation in every sense of the word.