ED25519 Child Key Derivation Let's say I generate a keypair for a user with go's ed25519 package:

pub, private := ed25519.GenerateKey(nil) 

And I want to generate additional child keys as signing identities for my user. Is it more secure to not use that public key created at initial generation and instead derive a new child private key as a signing identity? Or is creating another child key exactly as secure as using the public key created at generation?
A general common technique is used in PGP 
"key rings" or "key chains". You generate a master public-key pair and distribute your master public key. Use this master private key to certify your other generated keys so that you can store your private key securely, probably off-line, and use the other keys for daily usage. With your master public key, the certificates of the other generated keys in the chain can be verified.