Moving from one enterprise site to another

We have two DCs connected with OTV between and running Nexus 7k at core/agg and Nexus 5K as distro.

We also have a dark fiber from the active DC to the head office which is routed to where we have C9300 routers at corp site where we created office vlans.

The management wants to move offices and also we need to move the routers to the new office and order new dedicated fiber to our DC.

I am a bit confused here how we shall manage this without any downtime, the management wants both offices running until we have moved to the new one.

As we have locally created VLANs on the C9300 routers at current office how do we make that work with the new site at the same time so users can connect the laptop to the same subnets and both offices?

My first thought was setting up MP-BGP and VRFs or even Vxlan.

Anyone got any smart idea to make it as smooth as possible without downtime?