Go with a Speaker Selector, simple and less $$
Can I run all 7 indoor speakers on Zone 1, and just the 2 outdoors on Zone 2?
No, your 805's manual in the "Zone 2 and Zone 3" section on p. 101 will inform you:
"Connecting Your Zone 2 Speakers Directly to the AV receiver.
This setup allows
5.1-channel playback in your main room and
2-channel stereo playback in Zone 2, with a different source in each room. This is called Powered Zone 2, as the Zone 2 speakers are powered by the AV
receiver."
With that in mind, I recommend hooking up your Zone 2 speaker outputs (not the pre-amp outs) to a speaker selector box. Then hook your family room and outdoor speakers to this box--this is much less expensive than a second amp. There are many available for as little as $35-40 dollars.
FWIW: My home has a situation similar to yours (one receiver powering a main room + 2 deck speakers + 2 porch speakers). I use a SS4 Multi-Speaker Selector from Monster Cable to safely connect the deck and porch speakers. It is available at Amazon.com:
http://www.amazon.com/Monster-Cable-SS4-Multi-Speaker-Selector/dp/B00004Y3UX BeachAudio.com also carries several other selectors.
Like many here, I am not a fan of "Monster" as a company (high prices), but this little switch box is inexpensive, had good user reviews, and has worked as advertised for me. It has protection circuitry to keep your Onkyo safe. The operational "cost" of the protection circuitry is a little less volume (relative to the main zone) for your outdoor and family room speakers. But for background "stereo" sound in those locations, it should be just fine. At least it is for me, and my Yamaha 563 receiver is less powerful than your 805.
Good luck,