I don't think there will be any risk on the particular situation. USCIS will approve your father's case for the renewal. In the worst scenario, if something unexpected happen, then you will get the RFE from USCIS, then you can proceed as per that letter and then if the case looks complicated then you can hire an attorney

However, I personally suggest not to invest a big bulk of money for the lawyer for this sort of work.

***Only my personal suggestion ****