Yes, we booked the panama canal tour through the ship. It is pretty pricey, over $100 apiece. A good chunk of the price is the tariff for entering the canal, so I don't think you can do much better privately. Carnival says this tour sells out quickly so you should book it in advance. When we went, Carnival did not offer excursion sign ups online, so we booked as soon as we got onboard. They have since added the online booking on their website, and that should give you the price as well.