Hi Andrew,
I work in Rotterdam, commuting almost every other week from the UK (but via Dover Calais) - so:
Driving in Holland is quite restful - outside of rush hour which starts around 7:30 local time.
On this (and other) forum people praise the French motorway network, well Holland is at least as good if not better than France - certainly better signage and no tolls.
On that subject, you will find these words helpful when reading the overhead signs:
Gesolten - Closed / Blocked
File vrij - no hold ups
File X km - traffic queue of X km (plus it will show the town name where the hold up occurs or the road number)
The overhead signs also show the recommended speed for "good" progress in busy traffic - sensors and computer systems alongside the road automatically calculate the best speed for traffic to get through a jam without stopping.
Holland is not a big country, but do you want a single campsite for the whole vacation or multiple sites? Theme parks or beaches?
In no particular order, I would be tempted to stay at:
Rotterdam area
Delftsehout (www.delftsehout.nl) - family camp site located in a vast recreation park with childrens zoo - and easy walking distance of Delft city centre.
Amsterdam area
Camping Het Hof (www.campinghethof.nl) - near the town of Hoorn on the shore of the IJsellmeer (inland see to the North of Amsterdam) - this is a popular family camp site
Zeeland region (between Rotterdam and the Belgian border - about 1 hour in a car)
The Zeeland area has a whole load of great campsites - check out the reviews on the ACSI camping guides web-pages - good clean beaches with tall sand dunes.
Camping Zonneweelde (www.campingzonneweelde.nl) - family camp site with a great aqua-playground. Near the town of Nieuwevliet close to the Belgian border.
Camping Guides:
The Alan Rogers guides are worth reading, or read the ACSI reviews on the web (www.eurocampings.net) and ACSI DVD based guides (www.asci-gids.nl)
Theme Parks - Efteling (Dutch folk lore, fairies, etc) near the city of 's-Hertogenbosch is subtly different from the American theme parks - good fun
Theme Parks - Duinrell - also good
Robert