Claire,
You dont say when you are going, but in the "high" season anywhere in the region needs to be booked in advance.
We know where the site is, but have never considered it exactly for the reason you give, traffic noise.
we always stay at L'Etiole d'Argens http://www.etoiledargens.com/indexuk.htm, or you could try http://www.camping-les-pecheurs.com/swf/index.php?lg=gb, but L'Etiole would be the better bet for your childrens entertainment.
although on paper Les Pecheurs looks near to the A8, there is a huge rocky outcrop between the site & the A8, so traffic noise is not a problem (we often shop in Roquebrunne, & no traffic noise from the A8 is discernable).
As for stopping on the way down, we go via the tunnell & aim to stop around Beaune in Burgundy (first choice is the Municpal site in Beaune, but you must telephone them before midday to reserve a pitch, otherwise we use La Grappe D'Orr in Mersualt), Beaune is about an easy 6 hour drive from Calais, via Reims, Troyes & Dijon, but if you're traveling during August, pre booking your overnight stop on the way there & back.
GeorgeB