Lille is within easy range, they've got a nice big runway and customs also. Although they're lacking any sea-front, they are European City of Culture this year, so there's a lot of exhibitions etc going on. Have a look at
www.lille2004.com. They've also got some nice restaurants, so if you just want to sit around in the main square having a decent meal that's possible too.
Alternatively, if you decide to venture a bit further, my other half wanted to go to the Bordeaux Wine Festival which starts today and runs to the end of the weekend. Details on the
French Tourist Board website. The exhibition centre's within easy reach of the airport and there's a regular bus laid on for the duration. Might make a rather interesting trip if your passengers have any interest in wine.