I think I just answered my question. Instead of using igx-grid, use  igx-hierarchical-grid. Then set the hasChildrenKey property to a property on your parent object that returns true|false if the object has children.

Thanks, this worked. I did find a strange behavior that tripped me up a few hours. I'm using the angular directives. I had to change my HTML markup to get this working. I changed from <div> to <table>. It seems odd that this would matter.

<div data-ig-grid="gridOptions" id="employeeGrid"></div>

to

<table data-ig-grid="gridOptions" id="employeeGrid"></table>