Many people, here and elsewhere, assured me that all persons in a PNR will either be upgraded together or not at all. So I did choose the upgrade option and bought my tickets. I was worried about my US issued MC but the charge went through smoothly.
But there was a glitch: My wife and I were assigned seat numbers 5, 6. Despite the numbers being close, the seats are not. AFAIK there is no way to choose seats myself (eg, online), so now I am trying to deal with that.