You and he will be fine. You can run an 11-speed set up on 10-speed chainrings, and you can run a 10-speed set up on 9-speed chainrings.

For awhile, a lot of chainrings were rated as 9/10 speed. Now they have moved to 10/11 speed.

And as DOS said, your chains and cassettes need to match 10/10, 11/11.