My pet peeve at parks is when you park up and sit in your car for some lunch or a read and there is always someone who will park next to you and leave the engine running for the aircon - it may not sound much but its loud enough to be bloody annoying.
As for the boot camps at parks, these people are getting the use of a public resource for free and you can bet that for most of them it's a cash business.
What the government should do, is since obesity costs so much money in terms of medical treatment etc, allow a partial tax deduction (say 30-50%) of money spent on fitness activities - of course it will mean asking the trainer for a receipt which will force him to legitimise himself in terms of tax (IE actually pay some) so the government will probably get in as much tax as they give out.