Ahoy, Jayme!
Finding a spot to relax by the pool is certainly a quest every guest has to face! You'll soon find out that Disney Cruise Line asks guests not to "reserve" chairs with towels or other items, and they definitely have crew members who keep an eye on that. That being said, you will probably still see it happen.
On "at sea" days, especially, the early birds get the worms - I mean - chairs, by heading out to the pool deck first thing in the morning. You'll find that on port days, with guests heading out for Port Adventures, the pools are much quieter and you'll have a much easier time finding the perfect spot.
Our kids are eleven and fifteen, so they spend most of their time on the water slides or in the pool. (or at the soft-serve ice cream window!) There's no need for all four of us to have chairs, since they are coming and going so much. My husband and I usually try to get a spot for the two of us that serves as a "check-in" spot for the girls throughout our time at the pool.
Guests come and go during the day, so while you might not find a chair when you first hit the pool, there will certainly be some that become available when lunchtime rolls around and guests head to fill their bellies at the buffet.
I hope you have a most magical time aboard the gorgeous
Disney Dream, and I hope you have no problem finding the perfect deck chair at the pool! Bon Voyage! - Diane W.