That sounds like a pretty cool idea! I'm new to this myself, so I don't really have any input, but it sounds like a great idea! Maybe we could do something like that where I live, too! :)

Well, one thing you could grow is perennial violets (viola odorata)! Some like Royal robe and Queen Charlotte are very nice and you can eat them (and the leaves too). You can also make a violet tea with them too, it's pretty as well. They don't take much space, naturalize well and are fragrant. I love violets! Just make sure they are the fragrant, they are so much more enjoyable that way. You could also have a patch with 'tea' herbs and other perennials that you can make into tea, like agastache (great bee plant, if you have bees that is), florence fennel (a perennial herb that is licorice like in flavor), etc. Sounds like a great idea! You could also get black leaved elderberries (you can make pie with the berries, and the leaves are a black purple, very decorative), stuff like that.

Grapes -- I forgot about grapes --there are some wonderful varieties -- seedless and seeded alike. For just a seedless edible grape I love Himrod-- yumm.

Rhubarb! Gotta love rhubarb as a perennial stalk. So little care required. Old compost, sun and water. ;p
I grow both german and english chamomile and it makes great tea, very beautiful, small daisy-like flowers.
Bee balm (Monarda didyma) attracts wonderful butterflies and hummingbirds, and it is the ingredient that gives Earl Grey tea it's distinctive flavour.
Melissa/lemon balm is another great perennial; I use the leaves in salads and for tea.
All your mints are great for tea and dessert garnishes -peppermint, spearmint, etc but since they spread like mad you would have to contain them somehow. I have discovered orange mint and chocolate mint, pineapple mint. . .go find them and give them a try!
Most of your perennial herbs will do great for spices.
It is hard to go wrong with chives and garlic chives. They spread a little more each year.
Surprisingly, lavender is edible. There are lots of recipes for it on the web, too many to list here.

Good luck; let us know how it goes!

Talk to the people that run the edible park in Asheville NC
http://www.cityfarmer.org/ediblepark.html