Are they aware of what you've been doing? If so, tell them to keep you from any of it. Tell them not to let you have any of it.
If they're NOT aware, either way you can get rid of the weed and coke! What do you need it for? GET RID OF IT!!! Open the bags, and dump it all in the garbage!!! LOL Just get rid of it!
PLUS -- why are you going to a party with "slippery people?" Those people will certainly make you relapse. You aren't supposed to hang around people like that. You're supposed to hang around SOBER people. You can't change your parents -- but you CAN change your friends. Hang around with program people, NA people. They know how to have fun too. I had more fun with AA people than I EVER had with drinking people. In fact, I learned how to ski in my 40's with AA people!!! Before long, I was flying down a mountain at top speed!! It was wonderful -- until spinal problems put a halt to that.

But it was a blast! So stay with NA people, and away from slippery people!
And remember -- get rid of everything! Hugs, Lee