I'm confused by your use of the terms slash and backslash, but aside that there's another solution. grep takes any character as delimiter, furthermore it can modify files on the fly without creating any temporary files. Test it first in your test folder, but I think it should work:
sed -i "s:home/httpd/vhosts:var/www/vhosts:g"
and combine it with any other command (find, for ...) as you like to expand it to all 50 files.