Do Dumbo and then Speedway first. Why do I not say Buzz? Because you can always get a FastPass for Buzz later. You CANNOT get a fastpass for Dumbo or Speedway and the lines for these are jus ridiculous an hour or two after opening. Do anything that you can that is not FastPass on EE FIRST. Then hit the others.
You will be amazed at what rides you can get through during EE. It is a real time saver and well worth getting up for.
It really depends on your 5-yr old. With our DD, it was straight to Space Mountain. But if yours is interested in Dumbo, that probably should be first choice, as stated above, because there's no fastpass.