My husband and I were monogamous for a lot of years before exploring poly. We've been together for 17 years now, we started discussing non-monogamy about 7(ish) years ago. We have always had some openness to our relationship though, kissing and flirting were always understood as being ok for us to be involved in with others.
Everything will be ok in the end. If it's not ok it's not the end.