Hi Jon,
An eight-day vacation at
Disney's Old Key West Resort sounds wonderful! I love its laid-back Florida Keys theme.
My family also typically has a car when we are at Walt Disney World, and we do very often drive to the theme parks. Please to not misunderstand me, the
bus transportation at Walt Disney World is wonderful - it is nice to let someone else do the driving sometimes, and the buses are reliable, air-conditioned, and convenient. However, my family often finds that we prefer to drive. We find that it gives us more control over our exact departure times, and also makes trips such as resort-to-resort trips simple. At Disney's Old Key West Resort you will find that you can park very near to your villa, so getting to your car should be quick and easy. Especially when we had a little one like yours, my family would find that early in the afternoon one adult would leave the theme park and hop in the car to take our daughter back to our resort for a nap, while the other adult could stay in the theme park and then take the bus back to the resort later. As a guest at a Walt Disney World resort, you will be able to park at the Disney theme parks for free, which is a great perk!
I will mention that one place that we often do not drive to is Magic Kingdom. At Magic Kingdom, from the parking lot you can either walk or take a tram to the Transportation and Ticket Center, and then you take a monorail or ferry boat to Magic Kingdom. The buses from resorts to Magic Kingdom bypass the monorail or ferry boat step and drop you off right near the entrance to Magic Kingdom, so the bus can be more efficient in this case.
I hope that these thoughts are helpful for you, Jon! Have a wonderful time planning your vacation, and please do let us know if you have any further questions.