I like watching people experience these things for the first time, too. I have a 4-year old granddaughter whose only plane trip was when she was 18 months old, so she doesn't remember it. I'm planning on taking her on a one-hour flight from DSM, her home airport, to ORD and overnighting at the Hilton, probably in October. We've already tested the overnight in a hotel close to home; she LOVED the view of the river from the room and didn't even need to talk to her parents before bedtime. I figure there's plenty to see and talk about in the airport.
As for lounges- the first time I took my son (her father) into one, he was maybe 12 years old and reluctant. His father was a DYKWIA type and couldn't fly without a few drinks in him and maybe he thought that was how people behaved in airline lounges. After he discovered that they were just nice places to hang out, with comfy couches, less noise and a few munchies, he looked forward to them. I may have to spring for a day pass at ORD for the granddaughter before departure!