Tree Data Structure with DVR Arrays

I am trying to create a simple tree data structure using DRVs. I created a typedef cluster with the following elements:

Int (node's data)

Array of this typedef cluster (child nodes)

My plan here is to save the head node, and be able to iterate through the tree via the child node array. However I cannot dynamically build and assign an array of nodes, I can only add a static array. The following image shows the error that I get.

Any ideas why this would give me an error?

Thanks