How to get alcohol under 18 to bring to festival?
Well obviously you've given it some thought, asking strangers to carry your booze sounds plausible, but you be better with someone you actually know, who will a) be reliable & b) trustworthy. I'll assume you have e means to buy it, but even that is a risk if getting others to do it for you, as for hiding it? By this I hope you intend to leave it with someone, rather than under a bush!
Part of being young and stupid is figuring these things out for yourself. Good luck.
You'll be searched as you enter the festival, but once inside there'll be no shortage of people willing to break the law to sell to you.
Are you really asking us to help you break the law?
Do not disobey your parents. God is watching.