Doses can be tiny and diseases/conditions can be odd. Lots of non-FDA-approved uses of medications, because there aren't as many RCTs in the pediatric population.
Pediatric PK can be all over the place, which will affect drug dosing as well. Always double check your math, always. A 10-fold error (one decimal place) can be fatal with some drugs in the peds population. If mg is ordered, divide by patient's weight in kg to get the mg/kg dosing that is typically given as the dose in the Lexi-Comp Pediatric Drug Handbook.
I'm assuming you'll be in a hospital setting?
Primarily, I work in a pediatric ED (though lately it's been both adult and peds ED simultaneously due to staffing), with occasional stints in PICU/general peds.