See OH's rant kindly referred by TMR.
When the Dutch sites were run by Gran Dorado all the same facilities were there and ALL were included in the price. The only things you paid for above the quoted price was food, if you ate in their restaurants and cycle hire at 5 guilder a day (About a £1) if you wanted to use their bikes.
Fishing in the lakes, Use of Swimming pools, Gymnasia, play areas, sports facilities (Basketball, archery, football etc) all free of charge.