I would not want to wait for miles to post from a third party. Just buy miles, transfer from your account to his (gift miles), or transfer in from an hotel program etc.. if that is an option. Just get it ticketed and then move on with life, it’s not worth the effort to do extra car rentals or hotel stays for 2,700 miles, and as this is an award reservation in a high demand period, you risk losing availability if you wait.