What kind of sites/things do you like? How will you get to the Netherlands, for how long will you be there? Any kids- what are their ages?
Lots of people say that Duinrell is good, but we decided against it as we felt we'd end up staying at the campsite as opposed to visiting places. It's really hard to find smaller places online, as google tends to just bring up the big places. Don't forget to search for Netherlands as well as Holland as Holland is technically 2 districts.
Nature camps are great, we stayed at 2 which I would recommend- place near Haarlem which was a friendly camp site in a great base for travelling to lots of places- Amsterdam by train and other touristy places. Also here was our children's favourite as there was loads of things for them to do.
We also stayed here for a week which was a bit different to the other two but again it was a good base and we needed a washing machine by this point! There was a little kid's club which I hadn't realised when booking but it was low key (craft, football, discos etc)