I did this trip in the reverse direction this past April and had a blast - the Canal is something to behold - how 90 year old technology is still very much in use today.
There are no laundries on board the sun but you will be offered at least twice the chance to have your dirty clothes washed for $20.00 - your room steward you leave you a notice and a large bag to full up - you get your clothes back within 48 hours - some of the people in my group took advantage of this and commented on how much there were able to stuff into the bag - we had two formal nights - the rest were resort casual
If you wish to view some photos of the Canal - here is a link:
There are a number of other albums from the cruise on that site also - you may have to register the first time you use club photo.
As for excursions - i did the Town and Country ship trip in Aruba, The Paos National volcano tour in Costa rica - it rained up at the crater - the Old Town/Tequilla tour in Puerto Vallarta and the Land's end and beach tour in Cabo - all other ports I just got off the ship and walked around the towns.
The weather was hot the entire trip and very humid and muggy going through the Canal.
Hope this help you get started.