If you've been together for, say, 2+ months then I think that you're ready for a trans-Atlantic trip like that.
And Christmas is still five months away! By then you might want to get married while you're here.
If you were in the US then I'd say that after two weeks into the relationship you'd be ready for a fun time in the Big Apple.
Are you aware that hotel prices in New York skyrocket in December?
January and February are slow months. You could come for Valentine's Day as an alternative.