Restaurant Networking Question for scaling footprint

Hi All!

I have a growing restaurant that is expanding from a main concept to an additional concept next door but with some shared footprint, like kitchen space. I have an IT rack that I plan to run the connect to for the second unit and would love some opinions on whether this is the right set up or if I'm poising myself for issues down the road.

I have a fortinet 80F with interfaces 1,2,3 feeding three switches for POS, Cameras, General Networking (respectively)

For this new concept, what I want to do is use interface 4 to run an uplink to a unifi 24 port managed switch. From there I'll split signal to the camera switch, 4 waps (VLANs) and 4 VOIP phones.

I also want to run another 24 port switch unmanaged from that unifi switch and run all the POS all of that unmanaged switch.

My question is two fold...any unforseen issues with running this setup? Would it be better to just get a secondary ONT and run an entirely new network? My hope is that one day I would be able to tie the POS systems together if needed (sharing printing and firing dishes etc)

The second question is lets say from the fortinet interface 1 goes to VLAN POS Network 192.168.192.xxx . If I run interface 4 to that managed switch with VLAN POS Network 192.168.192.xxx also...does that bridge the networks so I can share printers and POS across the units?

Hope that all makes sense! I've been working on a network map and will share when it's done.