Visiting some of the white villages would be a good use of a car in that area, though it would probably be helpful to spend one night away from Seville in the process.
Cordoba is the classic day trip from Seville, though it's worth an overnight or two, or three. That trip will be considerably faster by train.
Carmona's a good day trip. Perfectly doable by bus but I assume faster by car.
Do you have to spend all two weeks (except for the night in Malaga) in Seville? Andalucia's very large, and staying in just one city really ties you down. It's a shame to have that much time and miss Granada and Cadiz.
Edited to add: ViaMichelin estimates the driving time to Cadiz at just under 1-1/2 hours, so I guess that's not an impossible day-trip destination by car.