My kids' first J/F trip was HNL-EWR on CO BF at age 3 (him) and 6 (her). The FAs got a laugh out of my tiny 3 year old reaching for the seat control while lying on his belly on the legrest (pre-pushback), so he could move it up and down.
7 years later, my kids both know to charge their iPods and GameBoys the night before a trip - without being told. They have FF accounts on every airline we fly (except WN...not worth it there). My son asked if I could get him Gold status for his birthday (seriously!) so he could upgrade without me.
And when the u/g doesn't clear, they suffer in the same (mostly) silence that I do.
(Although I did laugh when someone obnoxiously tried to cut the line during AA PLT pre-board by loudly saying "excuse me, please - I'm in first class" and my son said "doesn't he know he missed his preboard and has to wait like the rest of us?" just loudly enough to be heard!)