The sidewalk would need to have a "footer" for a Ufer to be effective. With only a few inches of concrete above it would tend to be in a dry area.
Pull the permit early have the grounding rods and interconnect inspected and approved, then cover with the sidewalk. Make sure to have it noted on the permit or get a copy of the inspection report in case the inspector can't remember or you get a different inspector.
Just a point to remember: If you can make them fit, the ground rods can be installed INSIDE the building. This also elliminates the copper theives from cutting your wire.
If it was easy, anyone could do it.