Hi Barney,
I work in Rotterdam, commuting from Buckinghamshire almost every other week - and so I drive past Koksijde on a regular basis.
First of all, Belgium is a great country - good food and a candidate for the best beer in Northern Europe. And you'll get a great reception as long as you don't speak French to the locals - this region is Vlaams (Dutch) speaking.
English will do fine, Northern Belgium and Dutch people don't expect others to speak their language (it's usually a surprise for them when they realise I'm English - because my accent is "unusual")
You understand that these are seaside campsites, and if you haven't booked you may want to look at the Dutch ACSI web-site http://www.eurocampings.co.uk/en/ - De Blekker is supposedly quite quiet.
To do:
Brugge (Bruges) is a great city to visit, beautiful buildings, and interesting shops. The city square is worth a visit, maybe to sit and drink a coffee or eat a meal, some of the bars have over 300 different beers. Plus brewery tours.
Damme (to the North and East of Brugge) is also really pretty - a small village square with six or so restaurants and bars. Prices are more reasonable.
Koksidje, Westende, and all of the sea side towns are interesting in different ways.
Robert