Is Diffie-Hellman key exchange the best way to securely exchange SSH keys?

I'm designing the communication mechanism for end user devices that will communicate with a row of servers. My current plan is

1. on first run, a device will generate its own SSH key pair (RSA and 4096 bits)


2. the device will transfer its ID and public key via HTTPS (utilizing a valid certificate) to one of the registration servers


3. once confirmed, the device opens a SSH connection to a reg-server and receives the servers public key

Is this a valid approach, or would usage of "Server Authentication with Certificates" (DH key exchange) be the better == more secure way?