Any grape in 9a would have to be a muscadine variety - I'm 8b, they do great here. Too warm for blueberries or jostaberries. Likewise on peaches and similar. I have no serviceberry experience - considered planting some, but my understanding is that it grows too tall for what the original poster is seeking.
Suggest looking into rosemary - yes the leaves are small, but its hardy, fast growing, drought tolerant yet can suffer the occasional flood. You will have to protect it initially, they can break fresh stems tripping over the plant - but in half a season or so, it should be woody enough, and thick enough, that they can bed down right next to it for shade. Given just a couple years and some marginal pruning, you could easily have a plant 4' tall and as much in diameter.
I have beauty berry and mulberry too - not a problem in my pasture, WAY to quick growing and ultimately too large for the space proposed.
The other thing you should consider is your chicken's diet - when whatever is in season, if you can't effectively harvest, will be dropping to the ground where your feathered dinosaurs will likely consume it. Treats are fine, but when it exceeds 10% (by weight) of the daily diet, there's a real risk of nutritional imbalance.