Let your infant nurse or have a bottle during the takeoff and landings. Give your toddler a sippy cup.
Older kids can chew gum.
You can also make a game out of your child blowing through his nose while you hold the nostrils closed. Pretend that you're a blow fish in the ocean. It can really help to relieve the pressure. You pay only shipping and handling. It's the place for teens to explore colleges, careers, and themselves.