Originally Posted by
claimui
You can select seats for free once online check in opens, which is 48 hours before departure, regardless of your fare class. So just do that as soon as you can.
Big +1 to this OP - online check-in will open up in advance of the flight, and if you do it, they'll let you pick seats for your family free of charge during this process. Highly recommend you set an alarm and do this right as it opens, given your desire to keep the family all seated together!