i recommend a small backpack for prescriptions, important or travel documents and other things you cannot afford to lose. This way your hands are frfee and you don't have to wheel something around with you.
It's also a great place to keep a small purse. wheeling something around until the cabins are ready is an unnecessary burden.
The backpack is also great for carrying sunblock, towel, other essentials on excursions. Get one which is small enhough for your needs yet waterproof. It also is great for carrying things around the ship or to the lido deck or pool area.