No problem with ampage - varies much as in uk. A few sites may have reverse polarity - take a tester. Less than a fiver. Many sites also still use the continental hookup. Take an adaptor just in case. Very inexpensive from camping shops or ebay.
I've never found a site in Holland that don't have the normal blue/white socket, but take a 2pin adaptor just in case. Just go to your nearest caravan shop & buy a 'French ehu adaptor' this will do you anywhere in Europe if you need it.
English is widely spoken in Holland so I would guess if you phone or email the site in English they will tell you the amperage. Don't expect 16amp tho, maybe not even 10. If your equipment is modern, reverse polarity is not an issue. Do a search on this site for 'reverse polarity' threads & make your own mind up. Theres been an awful lot of incorrect, out of date info posted up about the subject.
Don't forget to leave a review of the French and other European campsites you have visited!
Advice as above already given - which site are you going to?
One site we stayed on in the province of Zeeland years ago only had 3 Amp, yes, that's right, 3 Amp! Didn't realise that until we tripped it, that was in our early caravanning days, we are now wiser, having learned the hard way!
You'll like Holland I'm sure, but then I'm biased as I am Dutch. If you have bikes, take them, it's the best way to get around, and equally, when driving in built-up areas, or walking, watch out for them, they have right of way EVERYWHERE!!
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.