We flew Delta from PIT to MCO last summer, with a layover in ATL.
We were nervous about how the kids (DD 7, DS 5) would react to their first flight. They each took a Gameboy, some books, a pencil and a pad. Believe it or not, neither child was at all frightened by the takeoff, flight or landing. In fact, they spent most of the time looking out the window.
My wife and I didn't build up too much hype before the flight; we didn't want to draw too much attention to it. A few days before we left, I explained a couple of things to the kids.
1.) When in the plane, keep your seatbelt fastened at all times.
2.) During takeoff, the plane will begin moving very quickly. It will be bumpy and noisy. This is normal.
3.) After the plane lifts off the ground, we will hear a loud thunk and feel a bump under our feet. That's the landing gear coming up. Again, this is normal.
4.) When we land, the plane will slow down very quickly. Normal.
As soon as we arrived at the airport, I showed my son different types of planes and pointed out their parts. I pointed to where the pilots sit. We even watched the ground crew load the baggage, fuel the plane, etc. When the pilots arrived, we watched them check the jet for flight.
I think the familiarity really helps, as most kids are scared of the unknown.
The kids were treated just like adults. We let them drink soda, use their tray tables, and lower the window shades. At one point I looked across the aisle to see my daughter sitting with her legs crossed, drinking a Sprite, and reading a book; it almost made me cry. She looked so grown up.
When we exited the plane, the co-pilot gave each kid a Delta trading card with a picture of the plane we flew on (we got MD-88 and 767 cards). They also let the kids stick their heads in the cockpit to see where they fly the plane.
It was a great experience! Good luck to you! I'm sure everything will go smoothly.