Well, it does about 30mpg if you are running it up to about 55mph - all goes a bit wrong from there on in.
We have a 1.9 l manual, petrol engine, which gives it reasonable (though not stunning) power for hills and the like. As an aside, if you were getting a VW van, I would recommend at least a 1.9 - the 1.6 is widely regarded as being too puny and I think you would regret it.
We did look at things like the Bongo when we bought ours, but to be honest, if you are going to do any camping - especially with a little one and all the kit they require - I think something like that would be too small.
The other thing is that the VW fits into a normal sized car parking space, the high up driving position is lovely, you can stop and have a brew anywhere you want (handy if stuck on an 'A' road in a blizzard perhaps?), and ........oh, I could go on about it all day
Ebay is a good place to look for vans - that's where we found ours, although we went round and saw it and made an offer there and then, rather than going through the whole bid process. There is lots of info on the internet about things to look out for (rust for example), and you should get something pretty good for £2 - 3k.
Ours only had 60,000 miles on the clock despite being 20 years old and was pretty clean inside - so something a bit tattier (but easily do uppable) and with a few more miles on would be cheaper.
Of coure you can't guarantee that anything you buy won't break down - but a big advantage on the old vans is that they are relatively simple to fix, although saying that - getting relatively simple things replaced (like exhausts for example) can require a bit of looking around!
Enough from me, although am happy to ramble on about this all day if you want :0