How do I ask my dad to play the violin or viola?

I currently play the cello and am learning piano with no teacher. I love the cello, but I really want to play another string instrument. My dad likes me to learn more and be smart in musical instruments, but he just payed for a required track uniform and an overnight trip to gocompete at a resort for school, so were tight on money kind of. I can wait until summer, but how do iintroduce the idea to him?