Drug Possession: 18 Year Old First Time Marijuana Case

My question involves criminal law for the state of: Virginia

I was walking to a friends house when i was stopped by a officer, he asked me if i had been smoking i told him i was smoking a cigarette. I had quit smoking marijuana a month and a half before but did not clean out my wallet. Thinking i had nothing to worry about i allowed the officer to search me. He found a very old little bag which had some remaining crumbs which i think was about 1/10 of a gram very very little. He gave me a ticket which told me to arrive on court march 8 2012 at 930am. I have papers from a drug test i took a couple weeks before the incident proving i am clean and am willing to take another urine sample if needed. I have report cards from my school about how i have improved academically since stopping.I have never been in trouble with the law except for a school fight when i was a minor.I would like to not get probation if possible because i am a senior and plan to go vacationing and spring break etc.This is where i stand and am wondering what my punishment could be, if i should plead guilty or not guilty and if i should look into getting a free attorney because my parents do not know about this charge and i can NOT tell them.

Thank you ahead of time for taking the time out of your day to help me.