Yikes, this is a hard question, but I forget that you will have already been at the resort and you can pack your luggage differently, AND it will be a different time of year than us, so IMO, They only let you bring a carry on that is "so big" -- they give you size... I don't know how strict they are, but this is a bag you have to keep with you, all over the boat. IF you can convince yourself to keep it light, and DO that, then I would say bring the weekender (don't you love it???) Meaning, decide what you need for TWO hours. That is it. Put that in the bag. You don't need all your toiletries, etc. Your luggage will arrrive before that. If it had been the time of year you are going, I would have brought my swim suit and coverup, flip flops, book, mug, sunscreen. MINIMAL toiletries. and left room enough to put my purse in it. THEN that is all I would bring on. It has a shoulder strap -- will that bother your arm?? -- but you can't over stuff. Because you have to carry it. to lunch, or to the pool deck, I would avoid getting in line for lunch as soon as you get on the boat. Instead, score deck chairs somewhere, and then change, let the big rush leave (have a drink) THEN get lunch. You can get food and bring it out to the tables outside. SO try to get a table first...
When is dinner seating? If it is the later slot, you have plenty of time to do everything and not worry about getting your things before you have to get ready, actually I think you have time even if you have the first seating, but that is only if you are going casual for dinner. I will definitely use it next cruise, just wont carry as much on with me. But I would hate for you to be uncomfortable... So just remember there will be lots of people, and there are stairs, and there are little lips in the floor in certain areas (since it is a ship) which may make the roller case harder.