I am certain that you will love the upgrade!
Whenever I've sold a used device, I've always used Kijiji. I have tended to keep my old devices, but I've never had any issues with Kijiji
Before you post & set a price, have a look on Kijiji to see what others are selling theirs for, and the condition they were in, just to get an idea of how much you should ask.
Enjoy & hopefully your wife's decision to go with Apple, won't be a contentious 😂
As far as the wife is concerned, she tried her hand at Android years ago and it seemed waaay too different for her not so tech savvy self, lol. So she is sticking to the Dark Side. And I know better to not stir up the contention on that...since I manage to do it in other ways somehow, lol🤣🤣
Congrats! There's a bunch of videos on YouTube with tips to try, but the first thing I would look into is the Routines and Modes feature, so handy to have.