It is always possible for OP’s son to gift the money to his parents once it is distributed to him at age 18. Technically, a Form 709 should be filed the following April; the excess over the gift tax exclusion ($30K if both parents are the donees) will reduce the son’s unified credit, which is currently over $11M.
The $100K inherited will not appear on any income tax return. Nevertheless, an upstream gift of the $100K would appear on a Form 709 filed in the year after the gift is made, but Forms 709 are not normally part of the financial aid process.
Any assets held in the parents’ names as of the date the FAFSA and/or Profile is filed (or presumably when the scholarship application is filed) would be treated more favorably for purposes of need based aid than if held in the student’s name. This is also true for parent-owned versus student-owned 529 accounts.
OP should have a quick conversation with a tax planning professional who is also familiar with financial aid policies. Receiving these funds at 18, some time after the original testator passed, implies that the funds are now in some sort of trust account held for the benefit of the inheritor. Timing could actually work here in the OP’s favor. Presumably, assets held in trust for the son would need to be disclosed and would be assessed as a student asset. However, once he reaches 18 he can give the money to his parents, thereby reducing its impact on need-based financial aid and scholarships.
Again, a quick talk with an accountant or other professional familiar with financial aid policies is warranted.