Why don't you do online check-in 24 hours before then you choose your seats and it's free to do so.
But, of course, the best seats will already have been taken by passengers who were prepared to pay to select their seats at the time of booking, and there is not even a guarantee that there will still be two seats together.
(This, of course, is a problem with all airlines that allow you to select your seats when you book the ticket, whether you have to pay to do so or not; those who book earliest get the best choice of seats).