I was in PE on AF a couple years ago, and the family in front of me made a mess that looked like that. The kids were old enough to know better (my guess was 4 and 6) and the parents never said a peep the entire time and clearly had zero shame about the mess the kids made I was also glad they were in front of me and not behind me since the kids were using the row of seats in front of them as pull up bars for a good portion of the 10 hour flight.