Very pretty! I love all of the rocks! The peafowl might bother your plants, but it depends on how many plants there are to keep them occupied. When I free-ranged there were so many plants that they could never focus on just one to destroy.
Penning them is a good idea, and you seem very into landscaping so you can incorporate the style of your landscape into an aviary. Aviaries don't have to be bare. Evergreen trees work well in an aviary. A big rock for the peafowl to perch on would be pretty looking, stumps, etc. http://bamboopeacock.com/Aviaries.html
If you get an adult pair of peafowl, you can raise up peachicks from them and then free-range the peachicks. That way you will always have some in an aviary just incase, but you can also have some free-ranging.
Wow. This has been fun. My aviary is finally finished. It has a covered hexagon. And open fly area with rocks and several perches. Plus a small tub with water for them to play in. It will eventually be part of my garden area with plants all around it. Can you identify the type of birds I have by the pictures? All I know is that the mother of these two was bred to a green peacock.