I wouldn't recommend wireless rear surrounds, even though the signal is wireless those types of speakers still need to be powered. Therefore you would have to run wire to the nearest AC outlet.
If you want only one receiver you will need to look for a receiver that has zone 2 capabilities. If you are shopping accessories 4 less, the Denon 1712 which is last years model can be had for a really good price. otherwise to place speakers on the patio you would need a home theater receiver plus an additional stereo receiver.
I see you want 7.1, unless you are an extreme audio fanatic, the jump from 5.1 to 7.1 will barely be noticeable. I would recommend taking a the money you would spend on the two rear speakers and upgrade the center, left, and right speakers. Those three speakers carry the bulk of the audio and very little is played in the rear.
If you have any questions please feel free to PM me or post back into this thread.
Also if you are in the Lafayette area I own "Acadiana Home Theater" a small home theater business and I give free consultations.