Try buying earplanes for kids. My DKs wear these earplugs and they really help with the pressure.
Chewing gum or starbursts work really well, too, to relieve the pressure build-up in those little ears.
Another thing I do is lots of distractions. One time, my DD and I looked through the catalog in the seat and "went shopping" while the plane took off. She didn't even realize that the plane had taken off until we were in the sky. (Yay!) My DD says to have her look at the wings, they do interesting things while the plane is going up and down.
She can pretend that the plane is an attraction at WDW. (You know, "The Plane Ride!") Sometimes the turbulence seems like a bunny hop on a roller coaster.
Well, my family also likes to ride the escalator at malls and airports, too. So, our taste in "rides" may be considered different.
Hope this helps.
Marie