Contact Scott Smith in New Hill, NC. He's a member and probably has the big equipment that you need.
Other option is to use a router with a bridge to surface them. Years ago "toolferonne" built workbenches using this technique.
I've done a slab on my CNC, but nothing that large. Yours will fit on my CNC, it's a 4' x 8' Let me know if you want to try that method.
Raleigh Reclaimed is interesting. How are their prices for planing and sanding the slabs?