Unifi USG or UDB -> Firewalla Purple / Optimal Configuration with VLANs in Unifi

Hi all,

I am completely confused. I am a software guy, i need to setup my home network with Unifi either UDM or USG (i have both). I need to create VLANs in Unifi in order to separate the IOT devices with my other home devices and computers, i prefer to create a separate VLAN for my kids and finally all the devices to be monitored by Firewalla purple. Can anyone suggest me the best configuration because now I am completely confused. 

My unsuccessful approaches were

Provider Modem Router <--> FWP (Router) <--> UDM : Not working

Provider Modem Router <--> FWP (Bridge) <--> UDM : Not working, does not monitor the connected devices separately, it monitors the complete traffic from UDM

Provider Modem Router <--> UDM <--> FWP (Bridge) : Not working since the FWP is connected to one of the UDM Network Ports, so it does not monitor the other three ports  and also it does not monitor the UDM Wifi Networks.

Can anyone please help on how to setup the hardware in order to have VLANs in Unifi and monitor all the connected devices separately from firewalla purple?

Thanks a lot