We like Belgium a lot, we have stopped on the aires at Ostend and Brugge.
The only campsite we have used is Camping Memling at Brugge. Not a bad site but I dont know how you would fare with an RV there.
There is plenty of room along the coast road between Ostend and Middlekerke if you fancy a spot of wild camping. Plenty of vans park up along this stretch of road, no problems for an RV, can be noisey though as apart from the busy road the tramway also runs parallel to it. On the plus side is that you are only 20 yards from a long, clean sandy beach. Can sort out some more info on this spot if you want it.
When travelling to Belgium we use Transeuropa Ferries from Ramsgate, a 4 hour crossing, but it saves the drive up from Calais. We have found their fares to be very competetive and you can overnight at their terminal if you wish.
If I can be of further help just ask.
We have twice stayed on this site on the edge of Ghent ( a lovely city that is a little like Amsterdam) and it was easy to get in to the city. The site is set amongst a landscaped sporting area - I don't like sports but this is near a rowing course, sailing lake etc. :thumb: