Absolutely 100% they are responsible for ensuring their facilities are safe to use. For example, tape and signs would have been useful for the play equipment to clearly advise of the regulations. If these were being breached then the police should be called in the first instance. If there were bylaws in place then separate actions could be taken against those breaching the local laws.
In regards to dog poo bins, this is something that is quite frustrating. Does the person emptying the bins work with someone else? If not then why couldn't they still be emptied? But as per the previous answer dog, poo bins are not necessary any more as the waste can be placed into regular bins.
One thing to remember is though, if you put a 15foot high fence with electric wiring and guard towers around the facility some of the mindless idiots flouting lock down rules will still find a way to breach any rules.