Thank you so much for all the great suggestions, ladies. Lakesuperiormom, your offer is so kind, but at this point I think I will probably try making a trip to an office supply store or someplace similar and taking a look around at their selection. If they don't have the large pencils, maybe I will try the triangular ones.
The golf pencils are an interesting idea, as are the markers. Right now my son usually uses crayons to write his name, and he does well with them; but I would like to try something with a finer point for more precision in forming the letters. I suppose we will try the large or triangular pencils and see if that works, and maybe experiment with a few different implements to see what ends up working best.
Thank you again!