Получить дочерние узлы довольно просто.

Не уверен, насколько далеко вы продвинулись в своем коде, поэтому вот полный пример с различными вариантами:

using umbraco.presentation.nodeFactory;

namespace cogworks.usercontrols
{
    public partial class ExampleUserControl : System.Web.UI.UserControl
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            //If you just want the children of the current node use the following method
            var currentNode = Node.GetCurrent();

            //If you need a specific node based on ID use this method (where 123 = the desired node id)
            var specificNode = new Node(123);

            //To get the children as a Nodes collection use this method
            var childNodes = specificNode.Children;

            //Iterating over nodes collection example
            foreach(var node in childNodes)
            {
                Response.Write(string.Format("{0}<br />", node.Name));
            }

            //To get the nodes as a datatable so you can use it for DataBinding use this method
            var childNodesAsDataTable = node.ChildrenAsTable();

            //Databind example
            GridViewOnPage.DataSource = childNodesAsDataTable;
            GridViewOnPage.DataBind();
        }
    }
}