It's too sad to hear that you have experienced something like that. Maybe there are also other people out there who have been in the same situation as you.
I have read from an article that a number of parents have noticed some airlines are charging more to sit down with their children, due to favored seating charges. The seating fees are becoming
“Sit with your children” charges which has been around for a little while, as a Wall Street Journal article from Nov. 2011 deals with the subject. A plane ticket guarantees that a person has a seat on the plane, but not necessarily the one they want.