The exact gear ratio will vary a bit depending on whether it has 700c or 27" wheels. Use Sheldon's gear calc and aim for something in the 65" to 72" range. It may take him a little while to get into it, but it's really not a hard gear to push and a few weeks of riding or so should recondition most reasonably fit folks.

As for ring or cog, well that's really up to you.

Oh, and no freewheel. It's just not worth it. The only time I've even wanted a different gear is on my mountain bike. I ride many miles to the trailhead and a higher road gear would be nice. Actually up until just tonight I had the worst of both worlds--A gear that I felt was too slow on the road and too tall for climbing...kinda sucked. Now at least I have the magical 2.0 gear ratio. In the spring I build up a flipflop and throw on a smaller track cog for good road speed.