Since this is posted in the RCCL section and you mentioned a Grand Suite, I'll assume you've already narrowed it down to one line. That will provide limited options. There are three ships doing full transit through the canal, all in October. You've got Monarch of the Seas on Oct 18th, a 16 day. Also, on Oct 26th there are two ships, Radiance (13 day) and Serenade of the Seas (14 day). MOS is LA to Miami, SOS is LA to San Juan and ROS is Dan Diego to Ft. Lauderdale. Then in Nov, they start 10 and 11 day sailings from Miami on Jewel of the Seas doing partial transit only and coming back to Miami.
I don't know which would be the best for your needs/wants but the 16 day Monarch looks like the best value. It priced similar right now to the shorter round trip sailings.
Hope this helps a little.