Personally, I think the entire 'gun' idea is way off base.
Wedding gifts are for the couple. Typically to get them started on their life together, especially if they are under 25 and/or it's a first marriage.
Anything gun related will be construed as "for her only", and may put up "road blocks" between you and her new husband. That is exactly what you don't want.
Buy them a nice bottle of wine or champagne. Then, MUCH LATER, you can hand her some ammo.
Think about it.
1. How would you feel if someone gave your wife a personal present when you got married, especially something gun related. It might be taken as "If this doesn't work out, then shoot the low-life."
2. And too, she may only presently carry because she's single AND going home to an "empty" apartment. All that is ending.