Even though the different IDs have been passed to the load method, it loads only for first child. I think this is because of it tries to load for first record only. Please see below code in red.

Code:
load : function(a, b) {
	b = Ext.applyIf(b || {}, {
	    action : "read",
	   id : a
	});
	var c = new Ext.data.Operation(b), f = b.callback, h = b.success, e = b.failure, i = b.scope, d, g;
		g = function(j) {
			d = j.getRecords()[0];
			if (j.wasSuccessful()) {
			       if (typeof h == "function") {
					h.call(i, d, j)
				}
			} else {
			if (typeof e == "function") {
				e.call(i, d, j)
			}