The one you found looks good. It requires >= 6V input, which your batteries will provide even close to the end of their life.
For the Pi 2's current consumption, Adafruit estimates 650 mA (with a WiFi dongle and heavy computation). For the camera, the USB standard allows any device to draw at most 500 mA. The converter you found is specified for 3A, which is sufficient with a nice margin.
One thing to consider though is how well the Pi handles powering devices through the USB ports. With the original Pi:s, it's often recommended to use a powered USB hub if the devices draw significant current.