3 Days is a lot of pressure for newbies, so do your planning now. Get your fastpasses going on rides as soon as they open up. The the My Disney Experience on your phones so you can do that and also reserve a table service meal. I'm going to suggest that you look into the following meal experiences:
O'hana - Polynesian family feast, with games for the little ones
1900 Park Fare - Buffet meal with princesses (Cinderella is present and while the castle is nice, it books 6 months in advance)
Crystal Palace - Buffet meal with Winnie the Pooh and Friends
Schedule these meals for early breakfast or for dinner, except Crystal Palace which is in the Magic Kingdom park and can work for any meal.
Make your fastpasses for rides. Do all of the dinner reservations now and the fastpasses. Some people just are happy with counter-service/quick service meals but when you're on vacation there are fun dining experiences here that require the advance reservations, many of these things book 3-6 months out so you may have to keep trying.
As for the parks, familiarize yourself with the maps.