I agree with @Critter-3 , if you have multiple 529 distributions, and you know that some of it is taxable, you add up all of the distributions and all of the expenses and enter them only once in the TurboTax (TT) program. Assuming the students are not your dependents, the entry in TT is much easier.
Be aware, if you have only one 529 plan, you may only take qualified distributions for the named beneficiary. You may not take money from that account to pay the college expenses of other grandchildren. Any such distribution would be partially taxable. But, you are allowed to rollover money from one beneficiary's 529 plan to another 529 plan with a different beneficiary.
