I think for an occasion like this paying for seat selection might have been the best option at the time of booking (presuming no status). There is a fair chance all sorts of things may change up until Saturday, and some of the seats may simply be blocked out. The best bet would be to ask at airport check in, but still check in online to the best available at the time, which you may just find happen to be two together after all. You could ask the crew or if others would be willing to move as a last resort, but hopefully a solution will appear for you before that. Congratulations, and good luck