Just join Asiana Club for each of you, get the PNR's when you book and you can select seats online. The website is kinda weird for selecting seats but it works as I was able to select seats on two ANA award tickets that I booked for me and my as a trial run on OZ because they actually have flights with decent connection times to HGH. We were able to select two side seats on the 767 and 777 back to LAX.