His wife is, with her own US$15,000 fee and US$1 million gift under the published terms. A son who is 21 or older is not an accompanying child under any employment-based category and cannot be included; he would need a route of his own.
Spouse yes with her own amounts; adult son not at all
Employment-based immigrant categories, which the Gold Card leads into, allow the principal's spouse and unmarried children under 21 to immigrate as derivatives. The official FAQ attaches its own amounts to each of them: a US$15,000 nonrefundable processing fee and a US$1 million gift per accompanying spouse or child. For the wife that means the household total is two fees and two gifts, confirmed against the page on the day of application.
The adult son is outside the definition. Derivative status ends at 21, and neither continued residence in the family home nor financial dependence extends it; the Child Status Protection Act can preserve a child's age in some circumstances while a petition is pending, but it cannot bring a person who is already 21 at filing within the definition. He would need his own category — TN if he is a Canadian citizen in a listed profession with an employer, a student category, an employer petition or, if the family chose it, his own Gold Card application with its own fee and gift.
Each family member is examined separately for admissibility.