Can I charge two iPhones using a car charger with two ports?

We have a car charger that charges iPhones before the iPhone 5 (like my mom's 4S). The charger also has a usb port so you can plug in something else. In this case, we're trying to plug in the USB cord to charge my dad's iPhone 5 while also charging the 4S. Is this possible? Can we charge both? Will it make everything explode?

Walmart sells dual USB port car chargers. I got mine for $10 but I only use it I charge my iPhone 4. Everything should be fine. Nothing will explode.

Everything will be fine