Something I always recommend with newbies or with people who are going with different age groups than they typically do......
Get a copy (or two) of a WDW guide. One of my favorites is the Unofficial guide, but it's big and has a lot of sarcasm. Birnbaum is official Disney, so that might work for you. Or, get a copy of the maps for the park. Give everyone a task of writing down MUST SEE's. You'd be surprised what different people's must sees are. My cousin must go to the villian store. DS must have Pooh breakfast. At some point, I must go to the Christmas store. What I've done is create a little "form" where I put on something like this:
One restaurant I really want to go to:
Three-Five Rides I really want to go on:
One character meal I really want to attend:
Shows I really want to see:
Extra stuff I want to do:
Things I don't really want to do:
Other stuff to know?
The other stuff to know is open ended. I've received "I want to eat at Chick-fil-a", to "make sure we buy Mt. Dew", to "remember a big pen" to "I want to sleep in more than last time", to "I really want to try those little boats" or "don't forget the pressed pennies".
Then, make sure you accomodate the "musts" in your plan. Make sure everyone is on the same page as far as time together, time apart, times to be awake and everything, then just have fun!
For me, I feel more comfortable making sure everyone gets what they REALLY want to do.