Given there is interest in this trip, and Brugges seems to be a good option, I will be taking this forward, so would like to get a feel for numbers and dates. I have found a campsite see link below:
http://www.camping-memling.be/The campsite has:
Chalets/Caravans & wait for it Gypsy Wagons 
rate for September is 63 euros a night (£55.18), they sleep 4 persons or 2 persons and three children, only sheets provided on beds. Plus one nights rent as guarantee/deposit
TrekkershutSleeps 1-4 bunks beds and double bed etc, 37 euros per night (£32.41)
Camping/tents12.60 euros (£11.03) plus additional costs for car eg 5 euros, check rates on link at site.
If there is enough interest and preference on one of the weekend dates, then I will contact the site and make arrangements for bookings, and set up a confirmed list, I will also arrange a book grouping for the ferry travel, hopefully being able to secure a reasonable discount. The reason I chose this site is that it was the only one I could find that had it in english all the rest did'nt so if you find another site in the same or surrounding area with similar facilities then let us know
Ferry prices for the 3 weekends in september are around £80 return, bear in mind will try and do a group booking and get a discount.