Hmmmm, I have a 17ft double hulled Ultra Jon with a 70hp Yamaha w/power trim that would fit everything you mentioned. My biggest problem is when I want to get into real shallow water or stumpy areas. My lower unit takes a beating and I have to go real slow. A Go Devil is the key there! But hunting three guys out of my boat would be a little crowded. I guess it would make a difference on how the boat was layed out. Example, if it's a hand tilled with out a console that would allow you more "hunting space". I didn't like the hand tilled so I have a side console. I also have front storage compartments. One for live well and the other is for anchors, ropes, etc. That means there's a deck in the front. This also takes away from "hunting space".
So, all that said, I guess 17 ft would be ample depending on the set up. You would also want to be cognizant of the beam and hull if you want to hit big water with e few guys, gear, dog, decoys, etc etc. "V" hull will ride better than a flat bottom in big water. The flat bottom goes in shallower water when hunting the marshes. As you can see, there's give and takes to everything.
My suggestion is talk to some of the other guys that hunt the area your going to hunt and see what they are using.
"I see dead birds flying"