Family Based Greencard

I applied family-based green cards for my parents within the U.S. after they entered the U.S. as visitors so I submitted both the I-130 and I-485 applications simultaneously. They had their fingerprint appointments done and then got scheduled for a face-to-face interview at USCIS' Philadelphia field office. My parents and I went as scheduled and to our surprise, I was told I, as the son, am not allowed to translate for their interviews and a third-party translate is required. On the verge of being rescheduled for another interview at least 30 days out in the future, the INS officer relented and agreed to see us again the same day in the afternoon. We went out and hired a translator from an immigration law office and did the interviews smoothly in the afternoon. Thank God!

Two points:
1) Hire a translator for the green card interview if your family member doesn't speak English (you, as a family, are not allowed to translate)
2) If for whatever reason, you need to be rescheduled, ask for a same-day appointment if you think you can be ready on the same day.

Good Luck