SW does preboard 4 and under - immediate family only. Also medical needs. We went with DD - 5 in March - she was given number 91 - all by herself, the line was on the other side of the room from the line for 60-90, so we gave her tag to Dad, since the plane was overbooked - although they said they were very strict that your number must match your boarding pass. DD was not happy that Daddy wasn't with the rest of us - she was worried he wouldn't find us. When it was our turn to board, she was quietly sobbing, "I need my Daddy". The boarding agent saw DH turning red - "Are you Daddy?", and pulled him out of line to board with us! We did get to sit in two rows together, DD5, Daddy and Mom in one row, DD11 and DD13 in the row in front.