Actually it should be Spurs... and next year it might just be :D
- The domain is 'ok', I mean by this is you dont automatically think of the URL if you were looking for a Charlton website be only because of the .net extension.
Contacting the club is a good idea, but also have you thought about contacting any sort of fan club? Getting their backing would be good... you could even offer a column space or something? At spurs on match-days there is an 'un-official' programme that goes up for sale as well as the official one... if Charlton have something similar then perhaps get intouch with the producers of the programme/fanzine and see if you can get a few mentions by them and then in return they get some space on the site?
Eitherway good luck with it if you do decide to develop it.