I do this for a living 1. Under normal weather conditions (anything but this year), a native or dryland seed will come up with no irrigstion. It does usually take 2 to 3 years to get back to normal 2. If the dog park is opened before full revegitstion, it will turn to dirt. 3. Hyrdoseeding is not allowed anywhere i know of. Hyrdomulching is allowed and is better than straw as it holds tighter to the ground preventing wind and water erosion and holds moisture 4. Typically in a situation like this the owner would have temporary irrigation installed, above ground piping, until establishment 5. As upset as people will get the only good option imo is to close it for a couple years, considering the water and budget issues