The first sixty minutes on board decide the whole flight, so plan for those, not the destination.
Board last if you can bear the stares in the gate area — every extra minute strapped into a seat is a minute a toddler has to get restless before the plane even moves. Save the new toy, snack or show for the moment the seatbelt sign comes on, not the walk down the jet bridge.
Pack a change of clothes for both of you in the seat-back pocket, not the overhead bin, and bring double the snacks you think you need — turbulence, delays and a refused meal tray can each add an hour you did not budget for. Chewing or sucking through takeoff and landing eases little ears; a bottle, pouch or lollipop works better than any amount of reassurance.
Lower your expectations for screen time on this one trip and no one will remember it in a year. What they will remember, eventually, is the window seat over the Alps or the excitement of a new airport — the tantrum in row 24 fades faster than you think it will.