My wife and i have just done the panama canal on brilliance of the seas, if you arrive early in the morning make sure you get a good position on the ship as going through the canal is great! we got up early to get at the front of the ship and it was well worth it. for us once in a life time! enjoy your cruise.
Mercury is one of the older Celebrity ships, we were on it down under in January and February and were well looked after. The accommodation and food are excellent as well as the main menu each night there is a list on the left page of options you might prefer to any dishes on the main menu and we both liked this idea. The canal itself is a sight to to see as you go through the locks at both ends. This link will take you to the live webcams at the locks just cut and paste http://www.pancanal.com/eng/photo/camera-java.html?cam=Miraflores
You will see the Centennial and sail under it as you go though the canal. This is a rain forest area so you might be unlucky and have rain but hopefully you will be lucky and it will be sunny. Our final destination was San Francisco and when we woke in the morning of the day of arrival there we could here the ship's foghorn sounding and yes they do get a lot of fog there but it cleared as we got off the ship and moved away from the dock area.