Firstly, I'm sure you already know this, but psychs are no joke.
Secondly, I absolutely love the fact that you're introducing them to psychedelics.
Now onto my little techniques:
If they're really wanting to try it out, you're going to need to give them some low doses to see how they react. What I do with new people, is I start them off with 20ug of acid (in your case it would be to give them around 200mg - 400mg) to give them a relative feeling of it.
On this first day, you should let them have a solid 7+ hours of sleep, and wake them up around 4am, and prep them for the experience. Explain/reassure them that you will be there throughout the entire experience. The reasoning behind why I say 4am is because the trip and the after effects can last 12-18 hours. This way, they will be tripping during their normal wake-cycle, so they won't necessarily feel the "I NEED TO SLEEP, IT'S TOO LATE NOW. I'M SCARED" kinda vibe.
After this is done, wait another 2/3 weeks for tolerance purposes.
Up their dosage to anywhere between 700mg to 1200mg (1.2g), but you will be able to discern a reasonable dosage from your previous microdose with them.
Outside your house, set everything up prior to the trip. Nothing should be left for while their tripping, as it will create unnecessary "anxious vibes". Also, MAKE SURE YOU'RE STONE COLD SOBER.
If any anxiety were to arise, switch on all the lights, make THEM wake up and pour themselves a glass of cold milk, and simply just have a conversation about memory that they look back fondly on.
This is just your little experiment. You are here to make them love and enjoy exploring their own conciousness. You are not here to give them a solid 2 gram dosage and fuck them up mentally, resulting in them disliking this wonderful substance.
I wish you all the best, my friend. Tell your parents that the weirdos on reddit are wishing them a safe and lovable trip!