Excursions with yound kids?

Hi! I'm taking my family on our first-ever cruise next week. We're on the Freedom, stopping at Nassau, Princess Cay, and Grand Turk. I have a 3 year old and a 5 year old. Can anyone tell me if I should bother booking excursions? Our options are limited due to the young ages, but I dont know if it's a better idea to just wander to a beach on our own. Any advice is greatly appreciated!