The spouse and unmarried children under 21 are derivatives and receive the same two-year conditional permanent residence, after which conditions must be removed for everyone. A child's age is calculated under the Child Status Protection Act rules and is not simply frozen by the investment.
The two dates that matter
The first date is each child's twenty-first birthday. CSPA can subtract the time the petition was pending from the child's age in some circumstances, but the calculation depends on the petition's timeline and on visa availability, so a child who is nineteen at filing is not automatically protected. Ask counsel to run the calculation with the real dates and to say whether the family should file sooner or file separately for a child at risk.
The second date is the end of the two-year conditional period, when the family files to remove conditions on the strength of the project's job creation. The whole family's permanent status rides on that later petition, so the investor should insist on knowing what job evidence the regional center will supply then. Derivatives receive permanent-resident status on the same terms as the investor and may work and study without further authorization once admitted; that is a genuine difference from the nonimmigrant categories, and it is one reason families choose this route despite the wait.