My kid deleted the game & I can't remember if I used a google account or trainer club to log in. I've tried both but still can't get the game with progress back. Is there any way to tell which one was used?
The only way to tell is to log in with every account you know you could have used. With GMail you could use the google website to check which apps you allowed to access your info. If Pokémon Go is in there you most likely have an account there. (If not you should check it anyway. It's just quicker, if you find a google account with Go having access.)