Sherrie, good point about not overbooking excursions when you're a first timer.
My Sil insisted on doing this on our last cruise (their first) and then they complained they never had time to explore the ship!
We only had 2 excursions scheduled and enjoyed the Explorer and all her glory! The other ports we did on our own, had plenty of time to do so and enjoyed our day (we weren't overly tired for dinner either!).
My advice would be to figure out which ports interest you the most as far as excursion offerings go and explore the rest on your own.