since your are the principal applicant and your spouse and son are derivatives, CIS won't grant AOS to your spouse and son unless your I-485 is approved. Most likely the interivew will be adjourned. I-864 is for family based immigraiton. You don't need to file a I-864 for yourself. Legally it's not required that you file I-864 for your spouse and son. In addition, you're not a lawful permanent residnet or U.S. citizen and you're not even eligible to file I-864.