Generally speaking trafficking is bringing something into a place where it is not allowed to be

So in your first example, you are allowed to watch that kid, and both of you are allowed to be in that state and to see a movie, so no, you are not trafficking

Similarly if you are allowed to have that gun in both states then you are not trafficking. Additionally in the US if a case involves crimes across states it’s typically a federal charge and not multiple state ones

People can be trafficked against their will for slavery purposes or by their will as a form of illegal immigration. You can even “traffic” legal goods like cigarettes if you transport them without paying all applicable taxes. It’s a catch-all term for transporting things that a place does not want to let in. Typically the term is only used for bulk transportation, smaller amounts tend to have other more specific crimes