I wana learn a new instrument, but?

ok so i play the flute i have since 5th grade (im now going to be in 11th) and im really good at it but i wana learn a new instrument-mellaphone, when i started playing the flute my parents bought me a brand new one right away cuz they didnt want me to have to use a used one cuz they were afraid of the germs and now its summer and my band teacher has these lessons where we can go to learn the new instrument (i havent been making it to them cuz i have to work-ALOT-but he said he would like to meet up with me and give one to me(a used one) for i could practice by myself at night or watever) but my parents dont know that i wana learn this new instrument and im kinda nervous to tell them cuz they are all concerned about the germs and watever and im afraid that they are guna tell me no that i cant learn it, do you guys have any suggestions for ways to tell my parents that i wana learn this new instrument (cuz ik they are guna have some comment along the lines of omg u might catch a disease or something if its not brand new)