I think that inner part of your circular drive looks like a great place for a garden. You will love driving up your driveway and seeing your garden every time. And there's nothing wrong with growing tomatoes and squashes! Perennials are great, but it's also important to grow things you actually like eating.
As far as deer, I can only tell you what is working for us. We have a 5-foot perimeter
fence along the front of our 3 1/2 acres and a 4-foot fence along that back (the shorter fence was here when we moved in, and we haven't needed to replace it). Yes, deer can easily jump these fences, but we have 2 dogs inside our fence, so the deer give our property a wide berth. The fence is more to keep the dogs on the property so they aren't running the countryside chasing deer. So if you like dogs, that might be something to consider. One dog would probably do the job. We just happened to have a second one show up, and no one claimed her, so we kept her.
I also cross-fenced off a portion of that for our garden, because our dogs happen to be digging dogs, especially if they are after a gopher, and they also just trample willy-nilly over garden beds.
I'm having a hard time envisioning the exact dimensions of that area inside your driveway, but I read about a cool idea with gardens and chickens that I always wanted to try, but haven't yet. This would be for an annual garden. Basically divide your garden into two fenced sections, and put a chicken coop in the center, with a chicken door going out into each side of the garden. For the first year, you close one of the chicken doors, giving chickens access to one side of your garden. You don't plant anything there the first year (or plant chicken pasture there if you have time before you get chickens). On the other side of the fence, the part the chickens don't have access to, you plant your regular garden.
At the end of the growing season, you open the chicken door on the other side of the coop, and give chickens access to the part you just gardened. They can clean up crop residues, scratch around, eat pests, weeds, and weed seeds, fertilize with their
poop, etc. You close the door the side that they were on before, and that will be your garden for next year. You keep switching them back and forth from year to year, and they continuously improve the soil, while also being close to your existing garden for you to toss them stuff as you work in the garden. I would throw all of my
compost materials, fall leaves, etc in there too for them to scratch around, poop on, and compost. Remember the chickens will be in each side for a full year, so things really have a chance to break down.
I had fully intended to do this at my new place. Just the cost of the extra stretch of fence, and building a somewhat more elaborate coop for this is what stopped me. But something to consider. This would not work well if you have perennials in there that chickens like to eat.
As far as a thorny hedge to keep deer out, I'm pretty sure that you'd have a hard time getting blackberries or raspberries established without doing extreme protection on those plants themselves. Deer love them and will eat the young plants right down. I'm sure there are deer-resistant hedges you can plant, though. I'd personally rather have a fence than a thorny anything... such a pain to deal with if you ever change your mind or even just want to trim it back. And deer are probably harder to deter with thorns than one might think. I've seen them standing right in the middle of the meanest, thorniest wild blackberry patches, just munching away.
Good luck! Your place looks beautiful!