I would not worry first of all...that only adds to your stress and disappointment on not getting on a flight....

Every airline I have travelled non-rev on, and that's a lot over 30 odd years, has some sort of system to deal with non-revs who do not get on.

A lot has to do with the rules of the Customs, Immigration and Quarantine (CIQ) at your departure airport. In my part of the world (Aust/Asia), they rarely put you on if there is a good chance you will be bumped....but it can happem and I'm never content until the aircrafy starts to roll...
They will take your ticket and baggage....and yes you should take baggage as you have to wear something when on holiday....at the check-in counter as soon as you arrive if the flight is wide open OR after you have spent an hour or so biting your nails whilst on standby and waiting to be called and told you're on.....

Have back up tickets and always have in the back of your mind that you might not make it.....and stay cool...