iPhone 6 Plus & Pokemon Go

I have this as an old phone and want to give it to my nephew so he can play pokemon go. I took it to Geek Squad at Best Buy and had them do a full factory reset but still have the same issue. I log into my apple account and download Gmail and PoGo. The game will load to 100% then crash before the game opens. I've done everything i know of and to no avail. I'm sure it's something silly but can someone help me get this going so he can start living his best life and evolve his Charmander into Charizard :D

Also, he's only going to be using it while on wifi so i don't have a SIM card in it. Maybe that matters?

Thx in advance Y'all!!