Age rating and classification for our short film

My groups short film will be a reality genre and will be I think classified as a 15 as it includes a message that I think teenagers will need to understand and learn from. This is because in our short film we include a brief reference to sexuality so would be classed as sexual reference. We are using the idea of being a cross dresser/ transgender so it refers to sexuality and would again we would be trying to get the message across that being different is ok.  Although our short film could be classed under 12A aswell as we do not use any mild form of bad language, we do not include violence in any way, we do not involve any weapons or drug references either. I am struggling with it as we are including a lesson in our short film with a hint at sexuality and with the 12 A it has to be displayed in a joke way but we aren't aiming for our sexual reference to be a joke, we want to teach adolescents a lesson that its okay to be different.