Doing a on-off wireless network for a small restaurant and need some help. (Unifi hardware)

Networking isn't something I normally do, but I got voluntold to do this small project for a local restaurant's network. I didn't get to pick the equipment and it's already been purchased, so I am trying to make what I have work. Anyone know if this is possible and care to give me some guidance?

My equipment:

Unifi-AP-AC-Pro

UniFi Switch 8 POE-60W

Sonicwall Soho

I need to get 3 wireless networks up on that AP.

A network with a password for employees and the owner.

A secure network for the POS system and the credit card machines that is not accessible from the other networks.

A guest network for customers to use.

I have 2 out of 3 networks working, but I can't figure out how to get the secure network up. I created the SSID and it a vlan tag and also created the network on the unifi controller and gave it the same vlan tag.

When I connect to the secure wireless, it's like DHCP is not working and I get a 169 private network IP address.

I tried to tag the port the AP is connected to with the same vlan tag, but that seemed to move all of the SSIDs to the vlan.

Can this even be done with my current equipment?

Thanks, and sorry for the newb level question.