I don't see any downside to calling in and trying to apply the benefits to their reservation, but per the terms for legacy GoH, you have to "gift" the Free Night Award. If you're not successful, then make the reservation using your points and apply the award.

"If a Globalist gifts a Free Night Award to another party by booking that Free Night Award in the other party’s name in accordance with these Terms, the recipient will be treated as a “Guest of Honor” at the applicable hotel or resort. This means that the recipient will receive all In-hotel Benefits that would have been provided to the Globalist, had they redeemed the award for themself at the applicable hotel or resort. To apply Guest of Honor benefits to a gifted Free Night Award, a Globalist must make the underlying reservation by contacting a Hyatt Global Care Center and expressly requesting application of Guest of Honor benefits."