I took a look at google maps. There are two possibilities:
Either it is http://www.campingamsterdamsebos.nl/ or it is http://www.campingdewesteinder.nl
Both are close enough to Schiphol, but the second place fits redpaddy's description better (it is before Schiphol when coming from Hoek van Holland). But I am not sure whether this is a full camping site, the website is not very clear (at least not to me with my limited understanding of Dutch).
So I guess I'll tell my bro to go to Amsterdamse Bos. It is closer and for a single person with a small tent it is only 10,75 Eggs per night.