Quick question and recommendation

My wife and I are in a different scenario where she's not overweight and I'm a hippo (tm).  Additionaly she's not remotely competitive (which can be an asset).  If we go for bike rides and I drop her she's going to be super pissed so I have to focus on not making activity into competition.  That is probably your issue too.  If I beat my wife in a race to the fridge did I win anything?  Nope, but if I get her to come for a long walk then we both win. 

If you get the book from Jayne Williams http://www.slowfattriathlete.com/ that might be a good start to get in the right frame of mind.  There is entirely too much focus on "competition" in triathlon when in fact 90+% the athletes are participating.  Podium spots are limited to three and EVERYONE else get's a finishers medal.  So don't focus on time focus on distance and you'll be fine.  

When you start to train you'll absolutely need the support of your wife as training starts to suck up more time than most people would prefer.  A long slow bike ride will benefit you far more than fast and short.  If she's there with you it will 1000% better than if she's asking when you'll be back.  Trust me I speak from experience.   

Don't make it anything it doesn't have to be.  Skip the spandex, carbon fiber and gels and just start on your path to the race.  Things will come and people wil be here for advice when you need it.  Low and slow is how you start.  Don't increase too fast otherwise you'll end up hurt and on the couch.