We know this game is a few years old too, but Pokémon GO is still hands-down one of the multiplayer games for mobile devices. And it's not just iPhone either, you can play it with all your Android friends too.
PoGo has evolved so much over the last few years that it's now an excellent game with so many different things to enjoy. Catch and collect monsters, battle friends, go shiny hunting, take down gyms, battle Legendaries, or take part in huge "Community Day" events once per month.
Yes, go to any park on a Pokemon GO Community Day and you'll see hundreds of men, women, children, adults, grandparents and more looking down at phones playing Pokemon GO. It's still a huge game, loads of fun, and worth playing with all of your friends. Especially if Harry Potter is a bit too involved and convoluted.