As far as toasting at a wedding, I don't see the point to ruin the day for the bride and groom. Just hold the glass to your lips and pretend to drink or take a tiny sip. I don't care for the taste of champagne, so even if I were a drinker I wouldn't want more than a sip.
On the marijuana question, some people who use marijuana treat it like a religion and their goal is to get converts. I know someone like that. I tried it to make her happy and this was my experience: first of all I have asthma, so I couldn't stop coughing. Then no high feeling for 45 minutes or so. Then it hit me like a sledgehammer. I was dizzy and sleepy. I felt drugged, but not calm, relaxed or high. Half an hour later, I was back to normal. Now she is trying to convince me that a different strain of weed might work better, but I told her don't waste it on me. It is hard to keep her as a friend because her whole life seems to revolve around marijuana. She rarely talks about anything else. So I don't know how successful you will be convincing your friends to stop pushing marijuana on you, but good luck.