Research has demonstrated a clear link between perceived safety and children's playing outside. Clearly, there's more playing going on if their parents perceive the environment to be safe. They will also spend less time being sedentary, sitting in front of the television, etc.
The broad feedback to your concerns is that when we're looking at childhood obesity, we're looking at a multidisciplinary, multifactorial problem. I think the answer and the solution should also be multifactorial in nature. The individual parts of legislation will each have some benefit, and it's really hard, and it should not be an objective in a discussion like this, to weigh them against one another.
The true benefits of all those little steps, all those little parts of legislation, really appear if they come together in a combination. It's a multifactorial problem. It needs a multifactorial solution.