Advice: Cruise with guy friend and I have a boyfriend!?

My best guy friend of over five years is about to graduate college. For his graduation he has asked from his family for a cruise for 2 to Alaska this following summer. He has asked me to go on the cruise with him. Both of us are in relationships that are important to us but haven't been the greatest the last few months. We have a completely platonic relationship and just have fun hanging out together. He doesn't want his girlfriend to go because he knows he couldn't put up with her for a week or more, and it would ruin the cruise for him. I really want to go on the cruise with him to celebrate with him and of course for the experience. His girlfriend and my boyfriend are also not 21 yet, therefore they can not go on most cruise lines. My boyfriend and his girlfriend also understand the relationship that me and my guy friend have. I know to put myself in their shoes and believe that if the cirstances were the same and this was an experience for him that I could not participate in I would be ok with it. My parents believe the main issue here is trust and I know that doesn't need to be an issue between my guy friend and I. This is an awkward situation and I need some advice...any additional questions that need to be answered please ask! Thank you!