Pencils. 2H, HB, and 2B at least. A wider range is always better, but these three are the minimum you'd need.
Eraser
Colored pencils or markers (Prismacolor are fantastic, but also can be costly and are not at all a required brand)
            A few colors will be necessary, as each Pokémon has its own colors involved, but nobody needs to get a gigantic set of colors if they don’t want to. They can always simply be drawn in greyscale if necessary or desired!
Sketch pad; 8.5"x11" or larger
White and black colored pencils
A black pen for outlines (again, not mandatory)

Pokémon does contain some levels of violence, though it never crests into the realm of gratuitous violence. Some of the Pokédex entries have fairly dark topics (mainly Ghost-type Pokémon), but if anything becomes too much, we can always veer away from that topic and talk about different things.