Thanks for all the knowledgeable answers!
I'll be sure to have my boarding passes printed in advance when we fly out of Kansas City. When leaving Orlando we will have to print them there. I'm working on getting someone to check us in early though. (we aren't taking the laptop with.)
We will have a rental car for WDW, so we'll need to drop that off beforehand. I wish I could have found a ding for a later flight, as I think it will not be fun waking the kids up in the middle of the night to get to MCO for our early flight. Ah well, hopefully they'll sleep on the plane.
Thanks for the line tips. I don't care where we sit as long as each parent can sit by a child. Is there different advice if you have a B or C pass? I'm not sure we'll have A's for the trip home.