Doing your own thing is fine for those ports. No need to book a tour. Hairspray and the shows in the Aqua Theater are the most popular. No way to tell you which nights or showings are more popular.
As for dining away from the MDR - you can always find something that isn't extra-charge but it will be casual in nature such as the Windjammer buffet. Attached is a list of all the options for both Oasis and Allure.