I agree with the PP unless you have very young children,under 4, you wont be guaranteed A! We are a family of 6 and everytime we have flown, no matter how many are with us at the time, we fly SW all the time, we always get C and have a hard time sitting together. This time around my one DS's g/f is going with us and has never flown so I forked out the extra $$ for EBI, this way SW cks us in 36 hrs before hand, both going and coming home, then all I have to do, if I want to, is print out my passes at the 24hr mark! I like the peace of mind and not having to think about cking in and have the greater chance of sitting together!