Wow, my cake decorating skills are coming in handy today. :-)
That marshmallow fondant is a great recipe. You will want to try it on a real, full sized cake beforehand. Cupcakes won't be nearly enough practice. There is an art to it.
I've used a variety of different fondants. Most professionals buy fondant and each have their favorite brands. (Just do NOT I repeat NOT use Wiltons. It's really gross) However for you I would do the marshmallow recipe. It's easy to use and tastes pretty good.
Make things ahead of time. You can freeze the cake and make the fondant and frosting the day or two before. It will be enough work just decorating and you'll be tired from just doing that.
The poster that said many people don't like it is true. I put a good filling in the cake and a thin base coat and people do tell me that it is the best cake they've ever had, although about half don't eat the fondant no matter what fondant recipe I use.
Cakecentral.com is a great resource. However many used boxed mixes and frosting with crisco and powedered sugar and I would advise against that since it won't taste nearly as good. I make everything from scratch and an Italian Meringue buttercream. PM me if you have any questions. I'd be happy to help