France in June next year!!!
Perfect time to go as France is hosting Euro 2016. Although if you book after the 12th December and want flights to anywhere near where England potentially are playing, it will be expensive.
I would avoid Marseille - bloody dump and proper rough. Montpellier is nicer and Avignon is stunning.
You will find that between 10th June and 10th July, accommodation will be at a premium, due to the Euro's, but to be fair, the atmosphere will be great.
In the south, the host Cities where matches are being played are Toulouse, Marseille and Nice. They will have fans parks where matches are shown and there's always lots going on in between for a football mad youngster. I would avoid the fans park in Marseille though - we got tear gassed by the police last time we were there and chased round the City by the locals intent on killing us. It's not a pleasant place when there's football on.
Go and have a look on the UEFA site for dates and venues of games. The draw is not until the 12th December, before you ask where England are playing lol. (You won't get tickets either unless you are current members of the England travel club) but you could always buy from touts if he wants to go to a game. Approx £200 a ticket last time I was there.
To be fair, the way England play, we could be coming home before you even get to France.