The whole point of doing a SMaSH beer is generally to taste test a particular malt and/or hop. So go with whatever you're most interested in. EKG's would be a pretty standard choice with MO. I'd go with WY1968 for your yeast if you go that route.
For a Munich SMaSH, I'd go with something noble like Tettnang or Hallertau, or maybe a US equivalent like Mt Hood or Ultra.
If you want to brew a "Mocktoberfest", I wouldn't go the smash route. The best Marzen recipes I've tried use a combination of Pils, Vienna and Munich (some with a touch of Caramunich as well), and that really gives a nice malt backbone. If you want a good starting point, Jamil's Ofest recipe from Brewing Classic Styles is a great place to start.