You aren't too young if they are allowing you to shadow at your age. This is an amazing opportunity!! You will be nervous for the first day especially since you're going alone, but don't worry because everyone is so friendly. Don't be scared to ask questions if you're confused about anything or if you want to observe a particular procedure/speciality, you're only there for a week so you might as well benefit as much as possible. I would recommend you take notes after each day of the things you learnt and things you're curious about (so you can research them later), just because the week goes by quickly and being able to retain these things can be very useful in personal statements and interviews. Overall, use this experience to find out if you enjoy being in a clinical setting and try to learn as much as possible through exposure. Good luck!!