Sounds good to me. Nothing normal about poly, but if you want to here if people do this then, ya, they do. I don't see any read flags.
I taggged this "unicorn" not because you have one, I have no idea what you have negotiated around being able to date others etc., but because we say and hear over and over again on here that triads seem to work better for the long run if they are established as yours has been. There have been many come through these forums who are searching for what you have but not from friendship first but from wanting to date as a couple. I always suggest friendship first and what you have achieved would be why. It works better for many reasons.
Good luck. If something comes up, we will be here