Booked some flights for our family of 4 to go to KL in March next year. 2 Adults, 1 Kid, 1 Infant. I checked school holiday times (after the fact), and we essentially fly out before school holidays start and come back two weeks after, during the Easter weekend. I was after some advice, re: infant. She will be 16 months old by then, and we also have a rather precocious 3 year old (3.5 years in March). So far, we've booked the bassinet seats and paid for the row with extra legroom. Husband thinks we should book another seat for the infant/toddler. Not ideal, money-wise, but might be the difference between a good flight and a nightmarish flight.
So, given the travel dates, late night flight departing (not during school holidays) and afternoon flight returning (during school holidays), should we get a 4th seat? Do we have a good chance of getting extra room / seats if the flight isn't full?
I don't particularly like it, but have you tried OptionTown? You can bid for options such as (empty rows). Maybe just bid for a empty row on top of what you already have. I don't think the "Business class" bidding is worth it though. I've never been upgraded, but the parents have had a few business class (flatbet) flights on AirAsiaX.
There is a good chance of you getting a spare seat (in empty flights), but not if you have children with you. You will be preoccupied putting them into their seats. Generally hot seats don't sell out, but that is for Perth-KL flights. So you might be okay (spreading throughout the hotseat area (the chairs headrest is red).
Let me know if you need more help.