if Child 2 had private school expenses, could that expense be used against the 1099-Q
That depends. If CHild 1 was the named benificiary on the 1099-Q, then no.
If one of the parent's of child 1 and child 2 were the named beneficiaries on the 1099-Q, then yes, provided the parents' claimed the children as a dependent on their tax return.
