At CC they have towels available, usually there is someone standing along the path handing the out. If you go someplace else you may have to bring your own. I would think if you are paying to use the beach as part of your excursion they would provide the towels as well. Check at the excursion desk when you are on the ship.
Lunch is either you can sit down or do the buffet. We are usually running so we do the buffet or the snakes around the pool.
Have a great time.. We are going in April for the 7 day curise. I want to pack already.