mega 2560 power

Hello, I am using mega in my car to power some relays(6 of them) like this one http://i1134.photobucket.com/albums/m609/onlyforever702/Arduino/1ch5v.jpg and a 16x2, and a few sensors and leds... What is the best way to power all this? I was thinking of using a dc/dc like this http://i01.i.aliimg.com/wsphoto/v0/526465805/5-PCS-LOT-LM2596-DC-DC-Converter-Step-Down-Module-4-40V-to-1-5-35V.jpg, set it to 5.0V and power all that including the mega through 5V pin...