Depending on where you want to display the items and if you aren't iterating the whole sitecore structure you can get the child items recursively:
public static Result ChildrenRecursive(Item item)
{
var r = new Result();
var itemChildren = item.Children;
r.Items.AddRange(itemChildren);
foreach (Item i in itemChildren)
{
if (i.HasChildren)
{
r.Items.AddRange(ChildrenRecursive(i).Items);
}
}
return r;
}
You would need to modify the above code to suit your needs, for example if you need to have a tree object you would need a custom object with subitems properties in order to simulate the sitecore tree.
If you need to read over 100 items I would suggest building a solution using content search and setup indexing for your items.