Fade out over 0.5 seconds: TweenAlpha.Begin(targetWidgetGameObject, 0.5f, 0f);
Fade in over 0.25 seconds: TweenAlpha.begin(targetWidgetGameObject, 0.25f, 1f);
Since alpha is cumulative (parent alpha affects children), all children of your "targetWidgetGameObject" will fade out automatically.