Just an idea...but I wanted to do the same type thing in my own backyard recently for my little guy since I am a stay at home mom and wanted to have lots of fun and active things for us to do.
I used Craigslist to buy various items at steep discounts. We currently have a sandbox, water table, pool, swing along castle, cube with slide, basketball hoop with stand, toddler picnic table and a few other items, mostly name brand (like Step 2,) and paid less than $100 for all of it.
Living in FL, it will all fade as soon as you put it outside so I hate paying full price for such things. As long as there are no recalls, cracks, missing pieces, then this gives us a lot of options for not a lot of money. Plus, when my son outgrows something, I can resell it and then apply that money to the next items we want to try. It keeps us from being stuck with just one or two expensive items that my son might decide he doesn't really like on a given day.
So far this has really worked for us and my son loves our outside time. He's just under 2 years old right now and when he's closer to 4 I will see about finding a large, free standing swingset or fort type climber...but for now we have lots of options depending on his mood. He generally can play in our current setup for an hour to an hour and a half without getting bored or distracted.
Good luck!