Brian if you have a sharp inspector they will notice that grounding conductor is to small.
250.122(B) requires the grounding conductor size to be increased when the other conductors are increased for any reason.
In the case of a 30 amp circuit you need a full size grounding conductor, run 8 AWG hot & neutral and you need a 8 AWG ground.
You might want to use the 8/3 and ask the inspector if he has a problem with remarking the red to green or just stripping the red to bare.
Good luck, Bob
Construction & Maintenance Electrician