Lesson tonight...?

ok i have a riding lesson tonight and some of the other girls in my lesson only show up like twice a month. one of the girls that is away most of the time rides this gorgeous chestnut QH named CC who is an awesome schoolie and a beautiful hunter horse that is fun to ride. but on the other hand my friend who is in my lesson (shes one of the ones that actually comes to lessons) is riding a different horse then who she normally rides and she wants me to ride the horse she normally rides who is a 6 year old TB named Austin that is fine at walk/trot but bucks at a canter. im scared to rde him because he bucks and he is like 17 hh tall and is kind of intimidating.lol. my coach wants me to start riding a horse who can jump so i am limited to CC and Austin. who should i ride? if the girl that usually rides CC decides to show up, what could i do to stay relaxed and not get bucked off? lol thanks!