I've been trying to find the answer to this puzzle other places and I've been trying to figure it out myself and I just can't do it.
I think from the clues. You choose the following:
From: Los Angeles, CA (the time is right for the flight - 11:30 AM, and this is where Jack, Ben, (Jeremy's body) and Kate would already be, with Hurley and Sayid not far away from the commercials at least)
To: Guam (from the origami boarding pass puzzle)
Departing: 01/21/2009 (from date stamp on the photo of the driver holding the 316 sign, this could be the 20th or 19th based on travel times. The distance from LA to Agana, Guam is 6,089 miles. I checked on some flight from LAX to Guam for January 21 and the shortest travel time would be 14 hours and 40 mins. If you're flight was leaving at 11:30 am you'd have to leave January 20 or maybe January 19 depending on how many stops your fight would have. One of the flight travel times was estimated at 33 hrs and 45 min.)
Select Flight: 316 - 11:30 am (from the sign and from the title of the episode 316)
Promotional Code: 112 114 111 109 111 (translated from DEC/CHAR this is promo - http://www.paulschou.com/tools/xlate/)
Adults and Children could widely vary depending on who everyone is and who counts and who doesn't.
Adults: Oceanic Six (Kate, Jack, Sayid, Hurley, Sun), Ben, Jeremy Bentham (Locke). The body wouldn't count as a ticketed person. That leaves 6 adults.
Possible Adults: Frank, Desmond, Penny (and baby from one of the commercials, she wouldn't leave Desmond, but then Ben would kill her) Walt (adult or child).
Children: Oceanic Six (Aaron)
Possible Children: Ji Yeon (Sun wouldn't leave her behind), Walt (does he count as a child), Desmond and Penny's Child (if they go the baby goes)
Up to 10 adults (counting either Walt or the dead body as number 10) and up to 4 children (counting Walt and new baby). I have tried most of these combinations and nothing has worked.