Congratulations to both you and your wife for finally getting a Mewtwo! :D
If I were in your shoes, I would probably wait until another potential opportunity arises to get another Mewtwo with better IVs. You could use the 82% Mewtwo you have now as a means of accumulating enough Mewtwo candies so that if/when you get a Mewtwo with better (or perfect) IVs, you can power it up immediately. Then again, it's still a Mewtwo, not a lot of people have even seen or caught one. Who knows when that next opportunity will happen. :/