Benedryl can may kids sleepy or HYPER! Try it out at home first. Benedryl dosing is every 6-8 hours. One dose should be enough for a flight. I found my son was worse on the desent. I recommend earplanes. They have made a huge difference for him. No drugs needed.

Although it is nice if they fall asleep for the flight.

Walgreens even have a generic earplanes. I have not tried it as they didn't have kid sizes.