I am not a parent, but I would be more concerned with pills. Especially pain meds. They are way too easy to come by and incredibly addictive. My parents did not shelter me, and I only smoked weed and drank cheap beer. I also learned from my friends mistakes.
There were two dudes I knew growing up that did smack, they both OD'd on the first day of our senior year in HS. I never touched that sh1t. I also looked at how many lives of rock stars and famous people it ruined.
Being with one of my closest friends during a bad trip made me never want to do acid.
Crack was very easily obtained in the town where I grew up, but I never wanted to be a crack head.
I guess you just hope that your kids listen to what you tell them and hopefully don't get too fuked up. I say make them aware of the dangers of all that stuff instead of trying to protect them.
Lastly, to me, cigarettes are the gateway drug. How many people smoked a cig before doing anything else?
A drink a day keeps the shrink away - Ed Abbey