Just off the Koningsdam 18 day Hawaii (RT from Vancouver) last month. In the past we have mostly had fixed dining, but booked to late to get that this time. We missed having the same waiter each night who learned our preferences for beverages, but we had a great experience. We considered trying to make a reservation to get the same table each night, but didn't bother since we had planned to use speciality restaurants some nights. In the MDR we had a 2-top a few nights and shared tables on the other night ranging from 4 to 8-tops. We had wonderful dinner companions each time (even had the same couple twice - completely random). There always seemed to be a line up when the MDR opened, but if you waited 30 minutes or so it eased up. We were given pagers 2 or 3 nights but never had to wait long. One night the pager went off before the glass of wine I ordered in the Ocean Bar arrived!
A party of 5 might take a bit longer to seat so I would look into reservations if you are concerned.