#!/bin/bash
for i in */ ;
    do
        echo -n "$i:" >> "/path/to/some/file/already/created.txt" ;
        find "$i" -type f | wc -l >> "/path/to/same/file/already/created.txt" ;
        du -hs "$i" ;
    done
exit 0

Quick and dirty…
Actually this is quite slow when dealing with directories containing thousands of little files.
But it gets the job done.  I’ll play around with it and see if forking helps.