A.M.
Hello,
We just returned from Disney a few weeks ago(we've been multiple times over the past few years). At Disney - the Fast Passes are free. With the fast pass - you insert your ticket into a machine near the ride of choice and the machine returns your ticket with a fast pass. The fast pass will give you a time to return (i.e. between 2-3 PM) - but it's good anytime that day AFTER your return time. In terms of riding the rides - I'd recommend that you map out your day and figure out which rides you and your family really want to ride. Before our first visit, I purchased "The Unofficial Guide to Disney World" as it has some great ideas. I don't follow their "touring plans" - but I definitely take their advice on some of the rides. Also, 2 really good websites where you can gather some great info before your trip are www.disboards.com and www.allears.net.
Have a wonderful trip! - A.