There are plenty of options for cooling down a coop. Shade is definitely nice for hotter days. Maybe buy a tree from a nursery that has grown quite a bit and plant it nearby where your coop will be? A mister (a little ways away from the coop, though) may be a good option. Hanging a tarp over head somehow can help or buying one of those large shade tents from Walmart could help. We put a large, thick wooden board against the side of our coop and it kept the coop much cooler, but we are almost done building a new coop closer to the tree we have so it will be better.
I used to get those gallon ice cream pails, add water, freeze, and put a big ice block in the chicken run and wet it a little. It gets cool. I also did those $1 ice packs in different spots and they enjoyed it. Just a puddle of cool water nearby and they are glad to cool off their feet.
You might want to fence your veggie garden if it isn't already. Chickens like to help themselves =P