Will letting my kid experiment with drugs under our supervision be a good way to fend off addiction?

Absolutely not. I can't give a categorical no strong enough. First, exposure to the drug is often what leads to the addiction in the first place. They may do some with you, but also some elsewhere, and it doesn't take much to become addicted. Second, it's giving your approval that this is ok. That's a big line to cross over. And third, it's illegal, and can get you all arrested.
Absolutely not! If you have no tolerance for drugs, then nor should you for your kids. If this is true, introducing addictive chemicals to there brain is a sure fire way to start an addiction, not protect against. If they "like" drugs under your supervision, they will like them even more when you are not around, despite what they may tell you. Addiction is tough enough without help in creating it. Talk with them!
NO. One statement that i've repeated to my own children over and over again is: "the only way to be sure you won't become addicted to a substance is to not try it.".
Absolutely not!! This is illegal and could cause your children to be taken away from you and placed into child custody. The way to fend off problems is to love your children, give them your time and attention, listen to them and teach them the ways of a healthy lifestyle and show them good character so they can model themselves after you. Be careful to see that their friends are also of good character.
Are you serious? The subject of your question leads me to believe that either-1 you are a regular drug user or 2 you are already permitting this practice. In either case, your kids are doomed to follow in your footsteps. You really need to get some help if you want to prevent your kids repeating your mistakes! i hope you can find the strength to make this decision.