This is not a simple question. There are a lot of factors that go into deciding whether a juvenile's parent/ guardian needs to be contacted prior to questioning. Of course, if they have probable cause to arrest without the statement of the juvenile then the issue is moot. As for arresting without reading the juvenile his/her rights, that too is not a simple question and more facts would be needed to provide an accurate answer. I recommend contacting a criminal attorney if you have not already.
Rights do not need to be read prior to, or during, an arrest. The general public is very mislead about how your Miranda rights apply. There may be some issues if a statement was made to the police, but a lot more would need to be known.
Michael L. Doyle
This is not intended as individual legal advice and there is no attorney client relationship established by this answer. It is advisable that you seek individualized legal assistance. This is not a substitute for hiring an attorney.
There is no enough information to answer your question comprehensively. You should not post more information on a public website. Schedule a consultation with a lawyer in Philadelphia, to pursue all available defenses (including a possible suppression motion).