Pull your car across the sidewalk so a subject you want to talk to has to stop. An officer may stop and question a person when the officer has reasonable, articulable suspicion that the person has bee, is, or is about to be engaged in criminal activity. A stop is a seizure under the Fourth Amendment. On its face, most seizures are deemed unreasonable unless you satisfy a two-part test. Your justification of the stop will be in your report.
All case law starts with an officer in the field doing their job.
When you caused that individual to break from their path of direction by pulling in front of them your report will reflect the reason for the stop. Pulling in front is considered a stop. Pulling along side to talk is still up in the air. Your report will reflect why you told that kid to come over and talk with you. Telling constitutes an order to comply which requires reasonable suspicion.