as long as the M2-ATX's +12vdc rail can provide enough current for your laptop "travel adapter" then it should work fine. but even if it can't; you don't actually have to power it from the M2-ATX, you can connect the laptop travel adapter directly to the car battery and just use the M2-ATX as a startup/shutdown controller.
alternatively, you can build one of
these laptop auto-power-on modules, or buy one pre-built from 'W3bMa5t3r'. (you will have to configure the the laptop to turn off when external power is disconnected)
a carnetix PSU would be the best option for powering/controlling your laptop. they are expensive, but there really isn't any other product that provides the odd voltages that a laptop requires and also has an integrated startup/shutdown controller.
good luck, whatever you decide to do
