If you're talking about the new, dual band, "Quantum" router, you are correct. It does not currently have a guest network.
A marketing email from Verizon last month said that guest network support is planned for a future firmware upgraded. There was no date given for that upgrade.
That said, parental controls do not need a guest network. It is easy to setup controls for specific devices. If you post details of what you're tyring to do, I and other users here may be able to help you. Remember, we are users just like you and we only know what you tell us. The more details you share, the better your chance of getting helpful answers.