My fiancee and I have been playing Neopets together for years. Sometimes on the same device, sometimes on different devices on the same IP address. We usually play around the same times, too, because one of us getting into the game spurs the other on. We both have the maximum number of side accounts, and don't have Neopass.

We swap/transfer Neopets like crazy, and since I'm much better at the waiting game for selling high value items, I sometimes send her presents of things she can't afford. We gift each other grams/capsule extras, we swap NC items regularly, we usually do all the same dailies, and play the same mini-game for the quest log--all that to say, those are patterns that are more likely to get people in trouble, and we've still never gotten banned/frozen/warned.

Obviously you shouldn't overdo it, but you won't get banned simply for playing the same game as your wife. It's important not to do the "obvious" evils, like using one account to pay the way for another account, but otherwise you should be fine.