France and Italy are great choices. I'd highly recommend renting a car though...
Start 'em Paris. Then Dijon, Lyon, Provence, CoteD'azure (Monaco, Nice, Cannes) then into Italy... Milan (I'd skip it, personally)... stop for an hour in Pisa and wind up in Florence. If they have enough time, go down to Rome. If not, head back up to Venice. Instead of flying out of Paris, they could fly out of Zurich instead, and that way they can see Switzerland. So, north to Lugano, the Alps, then Interlaken then Zurich.