I'm trying to use this to populate a new site from a template. It looks like I have everything set up correctly from what I can tell.

The Template adds correctly and then I go to add the site and it gives me the error below.

Fatal error: Call to a member function children() on a non-object in /path/to/joomla/administrator/components/com_multisites/classes/dbsharing.php on line 112


Is there something I'm doing wrong or what? After I go back, it says it's created. No tables are ever made, nothing.

Your are not doing anything wrong.
I suspect a problem in JMS because some other customers have reported a potential problem like this one but they are not able to provide me a procedure to reproduce it.

I have added a fix in JMS 1.2.0 RC4 that may perhaps fix this issue but I am not sure and I have not yet received any customer that were able to explain me how to reproduce it.
For the moment, I am unable to reproduce and I have just tried to implement a rescue solution.

If you have a JMS 1.2.0 with a version RC4, I would like that you try to describe me a scenario that allow to reproduce this issue before updating to RC4.
To get the latest version , see the procedure in the FAQ www.jms2win.com/faq#sec-122

Hi,

I´m having a same kind of problem with following error:
Fatal error: Call to a member function children() on a non-object in ...administrator/components/com_multisites/classes/dbsharing.php on line 223

I tried to use another template for slave creation. My version is 1.2.0 RC2.

Start to update your version.
The current latest version is JMS 1.2.5 that you can update yourself as explained in my previous reply.

To get the latest version , see the procedure in the FAQ
/faq#sec-122