It shouldn't be too crowded during the week.
Tough call. If you want to have a full meal, then do the restaurant. It will cost less!
If you want to walk the WS and sample things from many different countries, then be prepared to spend quite a bit (especially if you are trying to make a true meal of it).
How tolerant is your 7 year old about waiting to be fed? Is noshing ok with her/him?
I'm not so happy with the FWF anymore, remembering how nice it was years ago. It's pretty tame now and rather boring.
So, for me? I'd do a restaurant. But, if I'd never done the festival before, I'd not be able to resist doing it.