Parking- For Conquest- Use EZcruise Parking in Galveston they are on line at www.ezcruiseparking.com
they are basically the same proceedure as the terminal parking (Which for a week cruise is $70)as you drop off your luggage drive to the EZ Cruise lot and they shuttle you back to the ship. EZ cruise parking will save you about $20 and they do offer other services (like car wash, oil changes, etc...
Excursions- if you hunt a little in these formuns you can find recommendations for excursions. Grand Cayman has many that you can book right there at the tender dock. But most have webpages and 1800 numbers... google on grand cayman tours and you can probably find them yourself. Same applies for Cozumel. not so sure about Jamacia, but I got to believe so.
The only caution I will give is that while the CCL booked excursions are more expensive than self booked ones, the CCL excursions garuantee you will get back on the ship before it sails. So, you pay for that insurance. It does not happen often that a tour has mechanical problems and is late in returning, but it does happen.
Good luck and have a great cruise!
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013