Brantly, until the OP clarifies ownership I think the most likely scenario is that the bonds are held in a custodial account for the minor child with the parent or grandparent as custodian, i.e. the child’s assets. I don’t think the bonds are likely to be held jointly (like a married couple would- each having 50% ownership). These kids are minors with assets they own but are kept in a custodial account with an adult named custodian.
If grandma owns the bonds (but they were transferred to her by the previous generation “for the benefit of the grandchild” than easy-peasy. Kid applies for financial aid, takes a package which is likely to include loans, after graduation when the payments start, grandma liquidates the bond and pays off the loan.
Not advocating this mind you- just pointing out that the titling of the asset is very relevant here.