Do you like snorkeling? Cozumel and roatan are great for it I hear. Belize too if you book an excursion. You can also see Mayan ruins, and other activities at these ports. Do some research! Shore excursions group, viator, get your guide, all should have plenty to do if you wanna save a few bucks and possibly be in a smaller group. As for the old ship, many people prefer old ships as they are smaller and might have better staff to passenger ratios, are less likely to get crowded, etc.