Hey reddit sorry for mobile formatting

I m(27) am concerned as to my nephew's and younger siblings getting older and what my parents, and older sister are doing or offering advice about for the coming years.

I tend to overthink these situations, I'm on the spectrum(specifically asperger's) and with of my family typically as cold and quiet, so it's hard to just directly talk to them about it.

But basically I'm afraid my sister(34) and father(59) wont be able to give accurate life advice for how things have changed in the modern era.

My nephew(17) is a senior in high school and I want to let him know that if he tries alcohol or anything at a party and isn't okay to get home, to call me and I won't be mad just want to make sure he's safe, but I also don't want to go behind my sisters back and give him the idea that he can party consequence free.

My younger sister(11) is starting to get closer to the age where people with less than good intentions can start trying to manipulate her, at our last family dinner she mentioned she had snapchat on her phone and felt myself scream inside my head. I didn't want to make a seen or call my dad out in front of everyone, so I stayed quiet, but I want to talk to my dad about making sure she stays safe online/or with people.

I'm just really feeling this concern because I view my nephew as more of a little brother and really want to make sure they're going to be okay.

Any advice would be helpful.