Hi Amy. You're right of course. There are a lot of forces that contribute to the problems of obesity -and not only for children; but they certainly are often the most vulnerable (and also a perfect target for remedial action since they are forming life long habits).
My thought though, is that to get the ball rolling, a simple plan is best. I think what you propose could be done in parallel or as part of a multi-stage solution, with an initial fast launch of whatever solution has the best chance of being adopted by the maximum number of people and producing tangible benefits. Other stages can then be rolled out feeding on the momentum and positive feedback from the fast start, or they can be launched as parallel 'sister' initiatives perhaps?
Projects that get too complex, or attempt too much at the outset, have a harder time getting off the ground, being adopted and adjusting to unexpected changes and circumstances. Longer roll-outs in uncertain economic circumstances can also leave good programs foundering when funding dries up.
I think if we want to make real change you create a road map for the long game but start with a quick spearhead program that gets things rolling.
There is a very popular chain of Spanish supermarkets here in Southern California called Northgate Gonzalez Markets. I haven't availed myself of the service yet but I see they set up grills outside (mostly holidays and weekends I think) and if you buy the meat they cook it for you. The idea of customer's buying the ingredients and having a cook or chef cook it up in a healthy way might be popular.
Another point is that among many Latino working communities the idea of 'comida por libra' (precooked meals) or 'cantina' aluminum pots where you pay for a week/month precooked food, drop off your 'canteens' in the morning (individual aluminum containers which stack together to hold a full family meal) and pick them up on your way home for dinner is popular.
I could see a supermarket tying in 'healthyfied' versions of some of these services.
I think this is a good idea. I think a twist might add additional interest. This could be one segment of the challenge or the main thrust: challenge each chef to create a healthy dish, of the culture or expertise of the opposing chef. So a fine French chef might be challenged to create a Creole dish, while the Creole chef who is challenging would get to create a French one.