Just got back a couple of days ago from 11 day Panama Canal on Jade. The bus did have a bathroom (only urine/no poop). Our ship was delayed getting into the canal so everything got a bit backed up. We were on the bus going to the ferry about 45 mins to an hour. Bathroom facilities on the ferry are fine. 2 women and 2 men. They are located on bottom deck only. There are a total of 3 decks. Unfortunately, due to our late arrival, our transit got delayed since we had to go through the locks with another ship since we missed our scheduled partner ship. Therefore, our 4 hour ferry portion tuned into 7 hours with a good amount of waiting time for the large ship to catch up with us. The total time of the whole excursion should have been 7 hours but was actually 10 hours! It was a very long day and we got back on the ship around 7:30pm or so. We were pretty exhausted but never regretted booking the excursion. After all, I took the cruise for the Panama Canal and I got plenty of time on it!!!
I would like to think that the delay we experienced is not normal. Have a great time and don't worry about the "potty" issue.