If you're going outdoors and need plan, contact
Meyer Sound, they will be able to show you products suitable for an outdoor Cinema, but it won't be cheap. If you're gonna go down this road, only look for manufacturers that deal with open air all the time, it will make your life easier in the future. Covered helps, but the atmosphere is in play.
As for receivers, something like the
Storm ISP can handle two zones of multichannel audio, with all the features you would need. It sounds like you need an installer to me, someone that can guide you through this, and AV installers that sell Storm will be able to get you where you want to be, again not cheap.