Sheraton Vistana Villas - shuttle question

[Infamousmare]

We're staying at SVV early December. Driving to FL, so will have our car and plan to drive to the parks each day (will have free parking with my AP). Additionally, we'd planned to make us of the shuttle to/from the parks, as my little one still takes naps and my parents/sister may not always operate on the same schedule as us. I'm certainly not expecting Disney transportation, but can anyone tell me more about SVV shuttle service? Is it on a set schedule? Do you just call when you need a pickup/drop off? Is it fairly reliable/easy to use?
TIA!