My wife suffered from airsickness. It made flying together an unpleasant experience, and airsickness tablets tended to cause drowsiness - so , she was either spewing, or sleeping.
I got her a 'Relief Band' and she now flies without airsickness, and with no side effects.
ReliefBand® -
In my experience, it has proven to be quite effective.
Good luck.
PS I just noticed there was a safety warning to keep out oif reach of children...but I figure if your child is using it, it will be under your supervision.