[If someone has their teenager sell drugs for them is the kid totally innocent?]
Under US law, yes.  There needs to be some evidence of intent to act in a way that violates the law.  This is not to be confused with an intent to break the law.  If the kid was coerced or lack the abilities to recognize what he is doing is wrong (or to use the legal term "not competent") yes, the kid is totally innocent.
[These are older kids running across the boarder... They knew.]
Source?  There is no way to conclude "these are older kids" without evidence when a lot (if not most) of them filed seven years ago when DACA was first introduced.  If the "16 to 25 years old" clients mentioned above would put them from six to fifteen years old.  Many of them might have been older kids when they entered but that still doesn't make them responsible or culpable.  Nor can you honestly claim they knew, especially as many (if not most) were smuggled into the country rather than "went under the fence."