Is it available for July 13

Yes the park is open from 8AM to 9PM, however they do turn the splash pad water off at 7:30PM. Anyone can go during the open hours. They have multiple covered picnic table areas and grills. They're in different locations through the park. You don't have to reserve it though you will run into others just visiting the park. Now for complete private picnic table you may call the city and pay a deposit for your own area for a couple of hours. However they do not exclude the public from the actual play areas. This will only keep people from sitting at your table. You may want to go look at the different areas for picnic setting they have many covered ones and quite a few away from the main playground area. Go through gate towards the restrooms and they have trails leading to the covered dinnin areas wit grills provided. The city can give you a price check on what area you want. The main playground area,splash pad you can't rent or have it closed to the public. Just the picnic area/grill

Should be open. If you trying to schedule a party or something you would need exclusive access to you will have to contact them.