What distance should I do?

I'm 14 with a good level of fitness and looking to get into triathlon. I do 6 or 7 training sessions a week with rowing and rugby so I am too busy and tired all the time to train. However August is off season for both sports and no school so I will have time to train. I don't know to do a sprint or Olympic distance as my first race. I have run 10k races before and I have cycled 40+k on my road bike and have had swimming lessons a few years ago. I do doubt my ability to put all these together at once especially with only a month to train. What are your suggestions and any tips would be appreciated. Thanks