Understanding Sacrifice...

Took the kids to the Armored Corps memorial at Latrun and while they climbed up and down the tanks and ran around the amphitheater, I thought about a larger question.
How do I explain to them the nature of the sacrifice made by the fallen soldiers whose names are engraved on the wall in front of which they were playing?
How do you help them understand that many of these names are of people who were 19 or 20 years old when they were killed and never "grew up" to have families of their own?
Or, had families with young children the age of Tonka and Paco and to which they never returned?
In societies like America and Israel where freedom from persecution can carry the highest "tax" possible, how do you help those who benefit so many years down the road actually appreciate that "freedom isn't free" and what was done for them before?
It's a daunting responsibility.
(And, on a humbling note, I was saddened by how many names had been added to the wall at Latrun since I last visited in 1991. Too many.)