Got it!
I modified function Grouping() to be this:
function Grouping() {
return (($this->iteratorPos % 6 == 0) && ($this->iteratorPos != 0));
}
and modified the relevant stuff in the template to be:
<div id="group1">
<% control MyChildren %>
<% if Grouping %>
</div>
<div id="group{$GroupNum}">
<% end_if %>
<p>Child: $Title</p>
<% if Last %>
</div>
<% end_if %>
<% end_control %>
Works like a charm! Thanks so much for your help. I'll post a link to the page you guys helped me make after its done!