I'll be at MCM, too! I did it a couple of years ago as my first marathon. You will love it. The crowd support, and the Marines' support, are WONDERFUL!
If you are on Facebook, there is a great group for people training for long distances: look for the Red Felt Run Club/MCMFT -- a group of people started it while training for Marine Corps back in 2011 (MCMFT stands for Marine Corps Marathon First Timers). It is a really diverse group of people of all ages and abilities. Very positive, very encouraging! You might check it out. My group run on Saturday is with a bunch of those folks.
Another benefit to long-running on Sunday is if you are a swim team mom -- my friends with swimming kids all complain about Saturday training runs because they have to miss out while they watch their babies tear up the pool.