Shuttle service to the parks?

[cruisingmickey]

Hello

Fiance and I are taking a Carnival Cruise out of Port Canaveral and want to fly in the day before to go to Universal (day of arrival) and to Downtown Disney (morning of cruise day). Planning on staying at the JW Marriott Grande Lakes but have heard mixed reviews about their shuttle service to the parks so my questions are: (1) "rely" on their shuttle or go through someplace like Mears and; (2) stay someplace else,closer to either Universal or Disney?

Thanks in advance