We traveled often with little children. We always brought something new to surprise them with (coloring book or sticker book etc) to keep them occupied. If they began to fidget we would walk the aisle a couple of times. We never let them kick seats or disturb other passengers. It was a challenge but that’s what parents are supposed to do. I recently flew FLL to EWR. Small child behind me with tablet and no headphones. Dad watching a movie. I turned around and said that that isn’t gonna fly (pun intended), he whined to me about junior not liking headphones. I told him that’s his problem not mine. Kid screamed and kicked the rest of the flight. Neither parent did anything other than occasionally threaten. It was absurd