Hi Laura! We are almost neighbors here in Indiana! I am happy to help you with our own travel plans that we have done successfully.
We have both flown and driven the route down to Walt Disney World and since we purchased a motor coach we are now driving more then flying so we know the route very well!
Since we are a bit further west then you we just hop right on 65 and head south so you will have to maneuver a few highways to finally hit 65. You can google the route that is the best and most direct or you can click
HERE to see a map. In a nutshell you will follow 65 to 24 to 75 to Florida Turnpike to reach your final destination! It isn't a hard drive at all and you only have to get through a few larger cities such as Nashville, Louisville, and Atlanta and since you will be taking the bypass around Atlanta that isn't even that difficult.
The entire trip is anywhere from 17-181/2 hours depending on traffic and construction. You will find going through Kentucky and Tennessee quite enjoyable with beautiful scenery along the way. We are a family who does not want to do it in one day so we stop a little more then half way down in central Georgia. That will take you about 10 hours. Then we get up early enough to do the last seven hours so we are at Disney by early afternoon. That timing works since check-in isn't officially until 3pm at the resorts or campgrounds and we usually can get right into our room/camp site. If you want to only go about half way the first day then you will find a nice stop just north of Atlanta. If it is a weekday you will want to make sure you get through Atlanta early before rush hour or mid morning.
If there is anything else I can help you with just send some questions to me!