Firstly, I want to let you know how amazing it is that you're taking the initiative to expand your learning! It's great you can identify that you have an interest in pediatrics. The internet is a great resource for learning - whether its information related to healthcare or a place to look for volunteer or work opportunities. YouTube has tons of educational videos on subjects related to medicine. As someone not yet in high school, it may be harder to find opportunities in a doctor's office, but don't despair! Ask the people around you for any shadowing or visiting opportunities they may be able to connect you to (school counselor, parents, friends, friends' families, etc.) You may also look into the doctor's offices in your area and reach out directly asking for appropriate opportunities to learn more.
I have a nursing degree and my time spent in nursing was so rewarding. Medicine and healthcare is truly a fantastic field and the learning opportunities are endless! At the same time, don't put too much pressure on yourself to learn all you can and take your time to discover other subjects, fields, and interests as well! The initiative you have is fantastic and I wish you all the best.