There are many commercial blueberry ales out here in New England, and some of them are actually decent
The base beer is almost always a clean blond ale that finishes dry, but not overly so. I'd keep it simple and not super malty. If you use MO as a base, then I wouldn't be looking to add any extra maltiness with additional specialty malts - the MO should be just enough. I think your original plan for MO/Oats/sugar with US-05 sounds solid. Either of your hop options will work. I'd keep the hopping relatively low, with just a 60-minute addition to get your IBU's.
I'm not sure when blueberries come into season out your way, but floating a few in the glass is definitely the best way to serve a blueberry ale. Bonus points is you can score some of the small wild-type blueberries.