If you wanted to try a cheaper older fire emblem game, there’s a couple on 3DS you could try. I really like Fire Emblem Awakening. It was my first game of the series on 3DS. You might even be able to find a used copy somewhere for a decent price. I know I got mine for around $30 a couple years ago. Fire Emblem Echos Shadows of Valentia is newer and I love it as well, but it’s mechanics are quite a bit different from most of the series. I definitely don’t recommend Fire Emblem Fates though. It’s not a bad game, but I find it overwhelming at times, the story isn’t the greatest and there are just way too many characters. I like to try to get to know them all but I just couldn’t due to the sheer number of them.
I’m sorry to hear about your loss. If your son ever gets back into either Splatoon game (I have both!) I’m always open to playing with others if he was ever interested.
Well I’m off to bed. Hope you have a great night. ^_^