Tough Questions

Lately, we have been having some deep conversations with Anna Cate and Brian about difficult topics like cancer, death, divorce, how babies are born, drugs and different lifestyle choices.  It has gotten to where Todd and I are just holding our breath at the dinner table every night waiting to see what that night's question will be.  Don't get wrong, I love that they are coming to us to talk and I don't want them to grow up in a bubble, but OH MY WORD this is hard.
Last week AC asked , "I know drugs are bad, but what do they look like.  What are they?"  I stood there contemplating: should I try to find pictures on the computer or wing it and give a vague description?  In the end, I did a little of both.
It's a hard balance of answering their questions, but not giving too much information. But how much is too much?
I would love to hear any suggestions,advice, or book recommendations any of you have.