I have a pretty...unique way of viewing Ethan and Lyra, I think.
I like to think of protagonists as not being canon because every player plays them differently (I think Bulbapedia takes a similar approach, too). The only thing that makes the protagonists canon is when and how they appear as an NPC. For example, Red is an NPC in GSC, HGSS, and B2W2. Lucas or Dawn in DPP, Brendan or May in RSE, etc.
But in GSC, Gold (and Kris) never appear as NPCs, so they themselves are not canon in the way that the others are.
HGSS changed this by having Ethan and Lyra as NPCs.
So to me, Ethan and Lyra are the canon counterparts of Gold and Kris. As such, I'd probably use the name Gold when referring to the protagonist and Ethan when referring to the NPC.