Sounds like a great trip. I thought your question about a hatch vs fan over the bed was interesting. I have wondered for a long time why I dont see more marine hatches and wind hood/scoops on campers? You can probably find a marine hatch that will fit the standard vent size, most hatches can be ordered with screens and even shades. Add a simple wind scoop when needed an you have a hatch you can peek out of or see the stars, or pull fresh air via simple cloth air scoop.
I've thought that if we had a camper built I would probably have it set up to fit a bow hatch large enough to stand up through, for both ability to do a camp check while safely up high and also roof access and all the other great things you get with that.