The immigrant investor petition fee and later the I-829 fee from the USCIS fee schedule, any regional center administrative fee, translations of the parents' records, and professional fees. None of these come out of the at-risk capital.
Keep the gift for the capital and fund the fees from elsewhere
The gifted amount should be reserved entirely for the qualifying investment so that the full threshold is at risk in the enterprise. Around it sit costs that must be paid separately: the petition fee set by the USCIS fee schedule (G-1055), the fee for Form I-829 two years later, and, in a regional center project, an administrative fee that is not invested and is often non-refundable. Certified translations of the parents' deeds, title history and tax returns can be substantial because the trace is long.
Legal and advisory fees for the source-of-funds narrative and the petition are private. Ask the project in writing what happens to the administrative fee and the capital on denial or project failure. If the parents intend to cover fees as well, a second, separately documented gift is cleaner than one lump sum that must then be split in the trace.