I would DEFINITELY get the Unofficial Guide to Walt Disney World, (you should be able to find it at any bookstore) as another poster recommended. It is the single best source of info on how to get the most out of a short trip, and it details every single resort, attraction, show, and restaurant (table service as well as counter service) in WDW. Tips for saving money as well. AND they put together these touring plans that allow you to maximize your touring time.
I would get the park hopper. On a 4 day trip, you want all the flexibility you can get.
As far as picking one parade as was suggested, very practical, but oh which one to pick! My favorites are Spectromagic at MK and Jammin' Jungle at AK. BUT you really should see the Fantasmic! nighttime show at MGM and Illuminations at Epcot, too. I'm not a big fan of any of the daytime parades other than Jammin' Jungle, which is amazing!

Stilt-walkers dressed as brightly colored jungle animals--not furry character costumes, but flowy, silky, shaggy, amazing costumes that evoke lions and frilled lizards and the like. And the floats are these amazing mechanical/ puppetry animals that you just have to see, IMO.
Remember, AK and MGM are each doable in 1/2 day (for most people). MK and Epcot, you can do 1 full day each, and then split another day between them.
I know several of us have mentioned 4 days as being a short stay in WDW, but don't let that discourage you. 4 days at WDW is better than 4 days anywhere else! You will come home with so many amazing memories your head will swim!
On arrival day, I'd definitely head to a park and take in one of the nighttime shows or parades.
Lots of kids (mine included) spend a lot of time in lines getting character autographs. At your kids ages, they might not mind forgoing this in favor of more rides, but I'd ask & decide it ahead of time before you find yourself mindlessly going along w/ the crowds.
Penny pressing machines: we collected these everywhere, then when we got home we glued them to a picture frame for our family Disney photo.
Have a great trip! Oh, BTW, did I mention how great the AK Jammin in the Jungle parade is?
