Hello @Lauren200,
There isn't a way to get a copy of a guest's government ID from Airbnb.
If their profile photo doesn't show their face you can ask them to send you a recent photo.
As you have instant book turned on you can, for future reservations, require that guests can't book instantly unless they have uploaded government issued ID to Airbnb. To do this you must have uploaded a photo of such ID youself.
Trust is a two way thing. You say that you hand over the keys on check in. How will the guest know that they're getting the keys from the host and not someone who's giving them without the host's permission? Your profile photo doesn't allow the guest the comfort and assurance that they're dealing with the host.
Steve.