Seaghan wrote:
Nuair a phósann daoine, deireanns 'chuile dhuine thart annseo
Go mairidh tú do nuaidheacht/ Go mairidh sibh 'ur nuaidheacht
A Seaghain, if you want to make your suggestions stand out more clearly against your comments, you might try using the bold [ b ] tag around them.

(It's in the forum rules.

)
nuaíocht can mean both "news" and "novelty". FGB has
Go maire tú do nuacht as "May you enjoy your new acquisition." I guess that's one way to look at it!
Joking aside, though,
Go maire tú do nuaíocht (GC) and
Go maire sib a nuaíocht (GC) are probably better for weddings.
What prompted this thread, however, was actually a request elsewhere for "May you enjoy your new life" in the singular for a very special context. Sorry, you weren't expected to know that. 