To playscape or not?

When Mike and I decided to go ahead with building this house three years ago, we were very careful about picking out our lot. He wanted a flat driveway and I wanted to be as close to the park as possible. My thinking was that if we were close to the park it would be easy for me to take two small kids in the stroller to play when the weather was nice. Also, I thought it would be nice to be by the park so then we wouldn't have to spend an enormous amount of money on our own playscape for the kids. I'm cheap. Well. I didn't factor into the equation the fact that we can't stay at the park all day long or the fact that our kids have energy to burn all day long. Right now, I still take them to the park almost every morning. But come dinnertime, I need for them to be able to go outside and play so I can get things done in the house. And they can't go to the park by themselves. Do you see the case I'm making here? We need a playscape. Currently, we have nothing of import for the kids to play with in the backyard. Left to their own devices, these are the types of activities I often find them engaged in when playing outside by themselves: 1.) Climbing the fence. 2.) Taking the liberty of opening the gate to go play in the vacant lot beside our house without telling mama. In bare feet. The vacant lot with fire ants, scorpions, snakes and rusty nails. (Our neighbor came over to tell me they were out there. Somewhat embarrassing.) 3.) Taking two of Mike's big heavy duty hammers and trying to hammer nails into our brick pavers. 4.) Getting the weed killer out and squirting everything they could find with it. 5.) I'm still not certain exactly what went on here but Emma came rushing into the house asking me to change her shirt and smelling suspiciously of gasoline. The back of her shirt was drenched. So I'm just gonna say they were dousing each other with gasoline. Anyway, you see my point? They need something out there to play with and focus on instead of using their imaginations. Because their imaginations seem to be very, very dangerous. I've been looking for free or cheap playscapes on craigslist. Me and about 1000 of my closest friends. It seems like they are claimed as soon as someone puts up the ad. So really, I just want validation that it's okay to spend $400 on a playscape right now. Right? For the good of the children? For their safety and well being? For my sanity? Thoughts?