The D3100 is a great camera, capable of capturing quality shots and challenging you on down the road as you delve into the world of DSLR. Check out my 365 thread and any of the pictures before 5/1 are from the D3100. In my time with the D3100, I shot several family portrait sessions, 2nd shot a wedding, won a couple of photo challenges, ALL with the D3100. Never a complaint, many an exclamation of joy for the results. Plus, during my courses at a local photo shop, I never once had a moment where the instructor looked at my pics and said "Wow, that must not be a very good camera." In fact, without trying to brag, my pictures were often used as an example during several assignment reviews because I really dove into learning the big 3 (aperture, ISO, shutter speed) and making sure I was doing everything right, and that was in classes where I was shooting alongside students with D7100's, a D3s, and a guy who had a Canon 5D Mark something or other.
Since you're not talking about going ahead and purchasing a 5200/5300 (or a D7100, or a D610) now, why not thank the wife profusely for helping you get your start in an amazing new hobby, learn the ropes while you frequently show off your improvement to her (thanking her again and again), and make the jump when you can? As you buy lenses, focus on quality glass that will also be able to move up to the FX world someday (if the bug bites you REALLY hard), and amaze your friends with fantastic shots that you capture because you know your stuff.
Really.
...and while I'm at it, thank the wife and gush over her generosity for buying you the camera that will be the starting point of your new hobby! And if you "annoyed" her, or hurt fer feelings. buy her flowers.
A happy and loving wife is worth WAY more than the difference between a D3100 and D3200. (trust me, I've been married to the same amazing creature for 22 1/2 years now)
Looking forward to seeing your pics, man!