With the help of my English-Irish dictionary and then checking with my Irish friends:
GRÁ GO BRÁCH
(pronounced gra go bra) is probably the best choice. Grá is love, and go brách is forever (as in Erin go brách). The accents are necessary. There are several words for love and for always or forever and Irish-Gaelic is slightly different in different parts of the country, but I'm told you can't go wrong with this translation. Congratulations and good wishes for the upcoming wedding.