If your friend wants to impress the sports at this club, show up with a decent SxS, like a BSS Sporter 20 with 28" barrels and slightly opened chokes.
I would avoid a Citori for ducks, even though my favorite O/U duck gun is/was a Citori. They have a tendency to get grit in the safety mechanism and become unusable. Didn't worry that much about it until my gunsmith told me he sees a lot of Citoris with that problem and recommends against using them in typical CA duck hunting conditions. Buy a Beretta, if it must be an O/U 20. Tell him to avoid guns with a scalloped frame, because they tend to develop cracks after a diet of duck loads.
I used to hunt one of those clubs when a friend had a membership, and there was a lot of pass shooting. Depending on location and density of clubs in the area, it may be tough to get ducks to decoy consistently.
