You've been together for a fairly long time. I would 100% be very upset not to go on a romantic holiday with my partner... I can't imagine what he's gonna do on that trip by himself. TBH I wouldnt want to be with someone who would do this at this stage in the relationship. If I were in his shoes I'd go on, say, a 3 star hotel trip for two rather than a luxurious trip for one.