Have areas where there is a rule of one doggy family at a time. An area to use for distraction training or if there's a dog in your family who doesn't like strange dogs.
Have a council officer/ranger at the dog park to monitor what happens there during peak traffic times and on weekends.
As others have said a BBQ area and plenty of benches.
Have a pond/paddling pool for the dogs with a concrete bottom to it (stops dogs getting stuck in mud).
Permanent agility equipment in a fenced off area. Again one family at a time (maybe have two enclosures) so the training isn't interrupted.
Plenty of shade, taps for fresh water (maybe tank water or something so there isn't any pressure on the town water supply? Have the water collected from the roofs of the covers for the BBQ area or something? Not too sure on this.
Poo bins with bags provided (just in case you forget yours) and more actively encourage people to clean up after themselves.
Umm LOL I think I've put too much thought into this!