Erika,
Most of our trips are two nights!The longest we've stayed is three nights!!!! Our next trip will be 4. Our son ,who was 3 on the first trip, does great! Actually, on our three night stay at AKL he cried and wanted to go home the last morning. He was "parked out"!
We have a three hour drive. If you have the money and the kids do fine on the plane, go for it!!!
We usually decide beforehand what parks to do in the mornings (when we are in comando mode) and then decide on what evening activities to do. Epcot is good "relaxing evening " park for us, maybe MK if Spectro is happening. We plan on one sit-down meal a day. We might skip a park every trip, but manage to hit at least three.