Oooh how exciting!!
I would have to say in MK a few rides/attractions that must be done are:
Carousel of Progress - this is mainly for the adults, especially your parents. This was Walt's project for the World's fair and was moved to MK. The girls may think it is lame, but for older folks it is a MUST do!!
TTA - is something that has to be ridden as well.
Of course seeing the castle is a must do. I recommed sitting in front after dark with snacks and just relax a bit. Take it all in.
For AK you must ride the safari attraction. It is very cool, everyone will love it. I also recommed the show "it's tough to be a bug" and festival of the Lion King. Great things to do.
If rollercoasters are a thrill EE is one of the best. Great theming and just enough "thrill" to get the job done, but not overly "commando" thrill ride.
Epcot I recommend Soarin' it is so cool, everyone should enjoy that one as well.
Of course there are tons of stuff to do, realize that you won't get it all done or see everything you want to see.
So study up on everything WDW and talk to the various people going, see what they remember hearing or seeing....this makes it personal.
Disney (for us older people) is sentimental, it brings back what you wanted when you were a child.
Have fun planning!! And have fun there!