Should I plead guilty or not guilty to my underage consumption citation? Do I need a lawyer?I don''t want to lose my license.

It was Saturday night and my friends and I were drinking. We went to downtown in Harrisburg and when we decided to leave we ran into a Sobriety Check Point. There was no way to escape it. The driver was under 18 and I was sitting in the back and my other friend in the front seat. Once we pulled up the cop asks us what are we doing, where are we going, and have we been drinking. We all say no to drinking. Then we all get asked to step out of the vehicle and the driver gets pulled out to do some sobriety tests. Then I get called to do a PBT test and I didn''t refuse to. My reading was .052. We all got underage consumption citations and the driver didn''t get a DUI. I didn''t know sobriety checkpoints are for everyone in the car. I figured its only the driver that needs to be sober so why did I get a PBT. This is like unreasonable searches/seizures. By the way they searched my friends car without asking anything and found a bottle of vodka.