The Left Bank or the Peanut Gallery have fast-food style options.
There will most likely not be time for a Chicago visit on wedding day (Saturday Oct. 5th) but if you wanted to go another day during the weekend or extend your stay, getting downtown is simple by hopping on a train at Lake Forest Train Station (Union Pacific North Metra website is linked here) . Once downtown, there are plenty of things to do: parks, museums, zoos, sporting events, restaurants, etc.