The only rows to avoid on an A319 would be 9 and 23 as the seats don't recline. You won't be able to sit in rows 10 or 11 as they are the exit rows. So, choose any of the others and they will be identical to row 6.

To keep your stress low, wherever you can get the 3 of you together will be the best choice, so that you are not trying to switch seats at the gate or with people on the plane.

Good luck!