What should we do about executive’s offer of special leave allotment?

Q. The daughter of one of our executive assistants was recently diagnosed with an illness that will require extensive treatment. Her boss offered her “a few extra weeks of paid vacation” to care for her daughter. He told her this before HR had an opportunity to talk to her about options for time off. We don’t think the special treatment would be received well by staff outside of the executive wing. Do we have to provide what he promised even if it’s against company policy? Is it even legal?