Steve on "Display Custom fields of first level children but not grand children"

So I found someone with a solution to a similar problem here:

http://wordpress.org/support/topic/display-certain-custom-field-from-each-child-page?replies=2

I have tried putting bits of the code above and the code from the link together but can't seem to get it right.

The problem is I only want to display the child pages and not the grand children.

i.e.

Main Page
-Child Page
--Grand Child
--Grand Child
-Child Page
--Grand Child
--Grand Child

Both the child pages and the grand children pages have a custom field called image. On the main page I only want to show the child pages "image".

Anyone got any ideas?
TIA