Can someone help: filing I-485 with imminent travale plan

Hello friends;

I have this problem: I have this travel plan made: Go to China this Saturday (July 21st). I would want my lawyer to file I485 for me ASAP. However, I heard from friends (I am not very knowledgeable immigration law) that if you are not physically in US while filing I485, you are at a risk of denial later on. Is this true? Can someone please help?

If so, I would prefer my lawyer to wait till I come back. But there is another problem: I (principle applicant) will be back to US on Aug. 11th but the rest of the family (wife + children) won’t be back until the Aug. 18th (one day passed the deadline). When is the best time to file?

Thank you in advance...