I've never owned a Traffic but I have owned a Bongo, which I found to be a really cleverly designed van but they tend to be 4x4 autos which are thirsty, they are also very small plus you cant walk between the front and rear of vehicle as the engine is under the seats.
They do have a good support network via the club and a good social scene, don't consider them as 4 berth vehicles though, due to the size as they're completely impracticable for 4.
Run a search on here as there has been plenty of discussion before or visit the club website Bongo fury
I'm biased too but I loved driving my Bongo, and I was a keen member of the owners club. Yes I would consider them small for a family, but they are ideal for singles or couples. Some excellent conversions available. It never bothered me about not being able to walk through from the cab as I invariably get out when I get to my destination anyway. Mine wasn't actually camper-converted, but it still wouldn't have bothered me getting out and walking round to get in the back. 4WD can be a big advantage on a muddy site, and I didn't consider mine to be that thirsty considering that it was a relatively big heavy vehicle as streamlined as a brick. I bought mine to replace a Toyota Spacecruiser, and compared to that the Bongo was extremely frugal with fuel, despite being bigger and with 4WD. Mine was the 2 litre diesel automatic. Bongos are very well equipped too, and even unconverted 8 seaters like mine come with lots of things as standard, such as an electric elevating roof and blinds on the windows.