Commercial Sand Digger
This sandbox digger is commonly sold to schools and playgrounds but is portable and affordable for heavy duty home use.  Built to last through time.  It is rated for age 3 and up but 5 and up will be able to use it better because of its heavy build and dimensions.  5-13 ages.. but you might catch adults on it as well.  If you want this digger in red color it is listed under heavy duty sandbox digger on amazon