I own this great 18W Dual USB Car Charger that can charge both my iPhone and iPad at the same time. Trust me, both outlets have been put to good use over the summer. At the same time. And the great thing is if you have someone else in the car, whether they have an Apple or Android product, it will work. You need your own cable to attach the charger to your device.
I would also suggest having a retractable cable for your car like the Lightning Tip Retractable Charger. It keeps your cable cord to a minimum so you aren’t tripping over it in your car.
Get both of these and you will be all set! Do I need to mention what a great Christmas gift this would be?