How to change from consular processing to Adjustment of Status

[ven4596]

Hi, my parents have the Green card interview in delhi consulate in June 15. They already have B1/B2 and visited US many times. I am considering to invite them to US this month and cancel the interview in delhi consulate and start the Adjustment of status in US.

Please let me know how big of a deal is to go through this and any risk factors in doing this?

Thanks in advance for your help.