The thing about peonies is that they're perennials. So they like to stay where they're planted .... If you're planting a permanent border/hedge thing somewhere along your vegetable garden (maybe intermixing them with rhubarb or something) then that might be cool .... But bear that in mind!
I plant calendula, cosmos, marigolds, sunflowers, zinnias, bachelor buttons, and nasturtiums in my vegetable garden. I actually save my calendula seeds each year and just broadcast them in the garden (HEY! Weeds I *like*! ) -- I also let dill come up willy-nilly in my garden, too. The flowers attract pollinators, and kiddos love picking them, and some do serve a good pest control assist too. I really like calendula because they are so hardy, I like their scent (they're a medicinal anti-inflammatory too) - when we have our killing frost, the calendula usually keep growing for several more weeks after the rest of the garden is black and dead.
You can plant pole beans around your sunflowers, and they'll climb up your sunflowers (so you don't need to make or buy a support for the beans). I haven't tried that with vining peas, I suspect they wouldn't work as well....
I've always wanted to try borage, which is edible (as are the nasturtiums, and people will grown and eat johnny jump-ups too).