We were there a couple of weeks ago, on a 2 night stopover on our way home. We were directed to the part of the park next to the canal, which i assumed they used only for stopovers until we got talking to someone who was there for 2 weeks (in a caravan). There were also a number of tents. The pitches in the main were big enough for large tents, (many of the caravans there for 1 night just reversed onto their pitches and left the car hitched ready for a quick getaway the next day.)
The sanitary facilities on this part were fairly basic, 4 toilets, 2 (i think) showers and 1 washing up sink all housed in a sort of portakabin. Presumably there as a temporary arrangement for the increased seasonal traffic. The permanent blocks weren't too far away though and they had excellent facilities.
There must be other parts of the site used for tourers though because we were in the restaurant and saw 2 units come in, heading for that area, later to reappear and go down a different road to another area of the site.
One thing you would have to bear in mind, particularly if you are in a tent, is that there can be very late arrivals and early departures depending on the ferry timetables, for instance, we were up at 5am ready to leave by 6am for the ferry port. I can imagine the constant crunch of gravel for that half an hour or so would have spoiled the tenter's lie ins.
Wherever you end up, have a lovely time, i love big family gatherings.