I asked a project manager who wandered by. She said that probably your best option would be to pour the concrete and set up the posts a couple of days before the build. Let the concrete set before you bolt all of the pieces on. She said your installers will like that, too since it allows them to make all of the posts plumb before you add the extra weight of the equiment on.
She also said be careful of quickset concrete. If nothing else, it's really expensive.
I can't speak to other equipment options. Has anyone else found a solution?
Setting the posts ahead of time can by risky, though. Most of those playground pieces fit within 1/8" so the posts have to be PERFECTLY placed in order to work correctly on Build Day. And then you would have to keep kids off slides, climbers, and basically any equipment that comes off the deck.
Maybe a better option would be to plan an Opening Day? Maybe 2-3 days after you build (or maybe the next Saturday), you could have a "Day at the Park" with food, music & celebration! That way, everyone can get on the playground & enjoy, without worrying about who's playing on what! And just like it's a great moment to turn the last bolt and be able to play, it's a GREAT moment when those kids (or adults!) finally get to pull the caution tape off the playground & enjoy!