Take the summit hops, then resell them to someone who likes garlic and cabbage and use the money to buy something you'd like to use. Seriously. Unless you like beer that tastes like feet, stay away from them.
I'd get some light Munich, and make an American Pale Ale with 90% pale, 10% munich, and featuring the glacier hops in a FWH & hop burst method. Either yeast would work with that. If you saw my talk at the NHC, use that recipe but swap glacier for galaxy. Since there will be an IPA and a cream ale, go middle of the road with the pale ale so you have something for people who want something more bitter than a cream ale but less hoppy and/or alcoholic than an IPA. Shoot for a 5% ABV beer, tops. Maybe 35 IBUs. If it's not different enough, add some medium crystal malts, lower the IBUs, and make an American Amber.
I like the English brown idea; Dark Mild would be good as well, as long as it was different enough from the commercial porter. You might see what kind of character that has and stay away from similar flavors. For example, if they're making a hoppy porter, you can make a malty brown and still be distinctly different.
An alternative would be an Irish Red-type beer. Yes, you can use the English yeast for that.
In picking styles, I'd say you are more constrained by what has already been selected than by the ingredients. I wouldn't want to make me-too beers when a spot in the style space has already been taken. Shoot for something different.
You didn't say what kind of event; without knowing the crowd, it's hard to say what beers to make. Don't want to go too aggressive/unusual for the masses. In general, keep things flavorful and drinkable without going too high on the ABV.