Is there a penalty if I fail to submit form I-90 to renew my green card within 30 days after my 14th birthday?
Don't wait more than 30 days.
Although late under the USCIS rules, a person who files more than 30 days after their 14th birthday could still have their application accepted by the USCIS. CITATION: Pg.4.Section.2.G1; http://www.uscis.gov/sites/default/files/files/form/i-90instr.pdf