reading your post again : the cops were given instructions to do those checks in France's worst collèges and lycées, of which we had given them the list. So, it isn't likely that the kid you saw was 10yr old, since collège starts at 11 or 12, and in these places, kids are usually rather 14 then 11, if you see what I mean.

About the Calva : if it was indeed 90 euros, even if duty-free shops are a scam, it must have been a very high Calva brand or vintage. I'd be interested to know what's on the label ?

CRC