There is no requirement that you be physically present in the US to file the I-526 petition and, in your situation, it may be preferable to file while you are in India. Currently, due to the volume of I-526 petitions filed, the current processing time published by the USCIS is approximately 14 months. After the I-526 is approved and a visa is currently available, you might choose to obtain your immigrant visa in India through consular processing. If your spouse and children are in the United States when the visa becomes available to you, they might choose to remain and change their status through the USCIS .
Once you enter the United States on your EB-5 immigrant visa, you may leave immediately provided you retain your U.S. residence to which you return within 6 months. Should you need to be out of the United States for a single period of more than 6 months, permission to return may be obtained by filing Form I-131. If you are out of the United States for more than one year without permission to return, the law automatically terminates your U.S. permanent resident status.