thames76 saidI would agree that you really should do it for yourself and not someone else or the mirror.
For losing weight, probably any exercise combined with a sensible diet will do. Since you already mentioned yoga, why not do that for gaining flexibility and losing weight? A normal, gentle hatha class probably will not give you any quick results, but if you go for something stronger like Vinyasa Flow or Ashtanga you can see results in both areas quickly. If you do the full Ashtanga primary series (around 90 mins) you'll burn around 700 extra calories, work your core muscles, get strong arms and stretch every part of your body. You'll have your legs behind your head in no time ;-)
Of course there's a downside: you actually have to do it - regularly!
I would suggest using Yoga in conjunction with an increase in your cardio routine. The hardest part about doing these is actually doing
Like everyone else is saying, don't do them because you want to please your partner. They come and go, and if he's with you in your current state, whatever it may be, he cares for you on a deeper level than just the physical.
It sounds like you're wanting to do 2 things: lose weight and increase flexibility. Cardio and creating a caloric deficit over time will help in the former and regular yoga (since you're already familiar with it) will greatly help with the latter.
A while back, I started doing yoga that incorporates the Vinyasa sequences and Astanga salutations 3 times a week and I can tell you that it DEFINITELY helps with flexibility. You just have to stick with it - that's the hardest part.