Simple, effective, aesthetic

You're driving and you want to charge both a tablet and a smartphone, "the coach load" of RAVPower (model RP-CC02) is the solution to your problem.
It has two outputs 2.4A at 5V (or 12W), each of which can power and charge a tablet (Apple iPad, Samsung Galaxy range or other) and of course a smartphone (less greedy a tablet).
But be careful of two things, the presence of two USB connectors imposes a footprint of approximately 40 mm h x W 28mm x W 35mm above the output of your cigarette lighter. So check that this space is available above the cigarette lighter of your car.

The "car charger" lights up (more precisely the contour of the USB connectors) a blue light when plugged in, which is handy at night to identify the connectors, but watch even cut contact your cigarette lighter is still powered, so be sure not to remove the "car load" when you go out of your car (although it is likely that few mA needed for the blue LED does not proceed to charge your battery) .
This is a simple device to use, efficient and aesthetic.