Thanks Mr. Obvious. With a pickup partner you don't have time to discuss extensions of every convention. This sequence does not come up frequently enough to discuss, therefore the basis of the bidding question is to see what the most frequent assumption of the meaning of the bids.
Open 2D (GF Ace asking bid), South then doubles 3S bid showing 2 aces of same rank, therefore the major aces. Then 7C should be odds on favorite make. Actually 7NT is odds on to make as well.