If you don't end up doing e-tickets, I don't think you would have any problems getting tickets. You have a couple weeks before Japanese schools get out and it gets really crowded. I don't know which hotel you are staying at but if it is a Disney hotel and you buy tickets there, you are guaranteed entrance no matter how crazy it is. Now if you are an AP holder and the parks are super crazy, that's a lot riskier! Have a good trip and make sure you buy a cheap fan when you get to Japan because it is so hot/humid already and it's not even full blown summer yet!