Took my 11 year old and 3 year old to the classic this year and would make the following observations.
The younger they are the less of the race you will see
Under 10 take the wife/partner ( see above)
Buy some earplugs which filter out the phrase ' how much further do I have to walk'
Take ear defenders.
Buggies don't work in the sand between Dunlop and Tetre Rouge, a large tricycle pushchair would be the answer.
The younger they are the quicker they will get lost on the campsite, 3 year old managed it within 10 minutes of us arriving on MB.
Plan some alternative activities during the day, Dad's awe at 30's Bugatti's, Bentley's and Aston's can wear thin on the PS2 generation.
You can't get p*ssed during the day, only after the kids are in bed, you need to be soberish during the day to keep track of them.
BUT, we had a really good time, and are thinking about the Classic again in 2006, but probably without the youngest.