There's a little thing at Walt Disney World called "The Goofy", which is exactly that - half on Saturday, marathon Sunday.  And several thousand runners complete it every year (I haven't).  I also know a few people who sometimes "double" - marathon on Saturday, marathon on Sunday.  Beyond that I will only say that proper training (Sat./Sun. runs that simulate the races) and proper pacing during the races are important.

One question.  Do you live near Cincinnati?  A lot of traveling probably wouldn't be the best idea.

Len

I have done some longer back-to-back races the same weekend, but certainly not with marathons and I would not recommend it.  Does not seem worth the risks, and you can let your local group know this spring that you are committed for 2013.  I guess it depends on your priorities (practical, physical, mental and otherwise).  It sounds like you have an emotional attachment to participating in the half in your community, which is certainly admirable.  If the Cincinnati event is a goal, however, then set your sights on that achievement for the time frame in mind.  You may not have to choose between the races depending on scheduling, but you have the advantage of experience and focus on training, so trust your own instincts. 

The PIG is a great race!  Lots of great advice above, it's your choice and the true is it's not a right or wrong answer.  Good luck!