Wow. That's specific. You do realize that you don't have to pick a field of medicine until middle of your third year at the earliest, right? You may get to medical school and decide that you hate children...or at least sick children. It happened to a lot of people in my class.
A pediatric intensivist is a pediatrician who has completed a critical care fellowship: A total of 6 years post medical school training. They take care of the sickest kids in the hospital (excluding the preemie babies who are in the NICU cared for by neonatologists). The intensivists (PICU docs) take care of a variety of different problems including trauma, sepsis, severe respiratory illnesses, end stage of diseases like cystic fibrosis and muscular dystrophy. They also care for post-surgical (mostly congenital heart disease repairs and scoliosis repairs) and post transplant patients. Most, but not all jobs are in academic medical centers and thus have more modest paychecks. They tend to take turns running the unit and taking call. Not a bad lifestyle if you can handle the stress.