If you have a different template for the children resources, you may use Ditto &filter parameter. Here is an example:
Let's suppose you have the parent "Page1" and the children "Page 5,6,7,8":
Page 1 (with Template ID 1)
---Page 2 (with Template ID 2)
------Page 5 (with Template ID 3)
------Page 6 (with Template ID 3)
------Page 7 (with Template ID 3)
------Page 8 (with Template ID 3)
---Page 3 (with Template ID 2)
---Page 4 (with Template ID 2)
Now you can use a filter which exclude all template except Template ID 3:
[!Ditto? &parents=`[*id*]` &display=`10` &filter=`template,3,1`!]
See here the documentation for Ditto filters, I think this is what you are looking for:
http://wiki.modxcms.com/index.php/Ditto_Parameters