My question involves criminal law for the state of: CA
My friends and I are planning on throwing a party next year (we will all be 21+ by then) and we wanted to have alcohol there. The party is going to be held at a place we are going to rent, not at anyone's house. Like I said, we were planning on having a bartender and alcohol present at the party. However, my other 2 friends that are hosting it with me want to invite some of their friends that won't be 21 by the time we have the party. We are planning on doing some sort of wristband thing to let the bartender know who is 21 (we will give these out personally) and for those few that aren't 21, we were going to mark them somehow (like they do at some 18+ clubs). Everyone at this party is going to be people that I/we know, not just a random "come one, come all" kind of party.
So, I have a few questions:
Even though we are taking steps to prevent minors from consuming alcohol at our party, if someone gets them a drink, are we held responsible? Is it simply because we provided the alcohol that we are held as the responsible ones, even though we will be taking steps to ensure that no one under 21 gets alcohol?
If the above is true, I plan on telling my friends that we either have to have the party with no alcohol or make it a purely 21 and over party. Otherwise, I will not be purchasing ANY of the alcohol for the party. If I do that but still help plan every other aspect of the party, if a minor is caught drinking, will I also be held responsible with my friends even though I didn't purchase any of the alcohol?
Sorry about this being so long, but I have been doing a lot of research and can't seem to get a straight answer. Thank you very much for your help.

