Advice on splitting up an Office Network between multiple new locations / COLO

Long story short, our company is looking at moving our office location to a building that makes more sense for our company size (we are greatly undersized for our current building). The logistics of the market dictate that we might not be able to find an office and warehouse space in the same location, and that we might not be able to move both spaces at the same time

This has led our IT Team to decided we are going to look at co-locating most of our network infrastructure at a hosted datacenter.

This excludes the obviously necessary gear for each of the new sites, Firewall, router / layer 3 switches, wireless controller and AP's, etc. We will be purchasing all new gear for both new site locations as most of our internal infrastructure is old

Currently our internal network addresses fall inside 10.0.0.0/8 network

Some equipment will go to either of the 2 new office locations, most will be in the COLO Datacenter.

Due to this split, obviously we would have overlap on subnets/IP's, which of course we could get around with NAT, but would a cleaner way be to simply re-IP the few devices going to the new office locations and carve out subnets for each, either in the 172.16.0.0/12 or 192.168.0.0/16?

The only networking devices needed at each new site would be a physical domain controller / DNS / DHCP (single box), Wireless controller + AP's, and some new switches.

We arent looking into private circuits between locations due to cost, so will be relying on a site-site tunnel between fortigates at each location

Has anyone been through a process similar to this and have advice / what you have learned to avoid during such an undertaking?

thank you all!