Erm, bear in mind that it's really hot here :P but I'll try my best!

I'd translate it as follows:


¡Enhorabuena! Os deseo toda la suerte y felicidad del mundo. ¡Pasadlo muy bien en España y haced que sea un día inolvidable!

Con cariño,

Pauline

So that's what I'd say taken into account what you wrote. We usually just say "¡Enhorabuena!" and left out the wedding (or whatever) thing since it's quite obvious most of the time.

Also, what I wrote is not formal, seeing as they're members of your family, etc.

Anyway, I hope it's okay and that they like it. It certainly sounds like a cute idea!

I don't think there's anything that we usually say when someone gets married, just congratulations and all that.

Hope it helps!