Bike conundrum

So I have the wonderful opportunity to getting a pretty decent deal on a Trek Bike but am faced with a dilemma on what I actually get.

Let me preface this by stating that my wife and I are both relatively beginner triathletes, first full year was in 2011 and we weren't really bikers before that.  Our plan is to do our first IM in 2013.

Currently my wife has a solid road bike, Madone 4.7 and hasn't shown a big interest on getting a Tri bike.  I thought that her first bike should be a road bike so she gets comfortable on the saddle.

For myself, I've have a basic Schwinn road bike that I've used for the past few years of occasional riding.  I purchased a Cannondale Slice 5 Tri bike (entry model) last year and definitely saw the improvements of going from my aluminum schwinn to the carbon fiber cannondale.  Also last year, I did my first road race which I enjoyed a lot and would like to do more group riding in the future.

So the question is, because I have the opportunity to get a great deal on a bike, what should I get?  

• I can get a higher end Tri bike for my wife in preparation for our IM.  I do think it would be in her best interest to get on a tri bike for IM.
• I can get myself a solid road bike that will serve me for future group and training rides (but probably won't be used for races)
• Or I can get myself a higher end Tri bike.  This would leave me with my schwinn and I would probably end up selling my cannondale (I only train on my tri bike currently so that may not matter much)

My gut is telling me to get the Tri bike for myself since I would probably get more out of it than the road bike (not sure how many group rides I'd actually do), plus I'd get some cash back from selling my current bike, but I do like the thought of having a nice road bike.  I notice that on these forums, a lot of people tend to train on their roadies over their tri bikes.  Any big benefit of one or the other assuming that you're mostly training alone or with 2-3 people?