In general, you get what you get and you don't get to pick. Remember that there will be a ton of people there. They will be using the whole wind through of Indiana Jones as the que, and will have stations to "approve" the kids as being old enough first and then two or three stations to give out the passes at the end. One time, we got a time that was the same time that we had just gotten celebrety autograph fast passes for, so they were kind enough to give us passes from a later time. But it is kind of frantic, a rush in the morning, and I honestly wouldn't plan on getting a certain time.
For the time before the "show" I think that it is 1/2 hour before the show time that they have you meet at sounds dangerously, but I'm not 100% sure. They'll let you know know when they give you your pass though.
ETA - think about it this way, there are 19 shows a day with 30 kids a show. Each kid will have a parent with them in line (and some will bring the whole entourage). And they will all book up first thing in the morning. So you have to figure probably over 1200 anxious people waiting to get a slip, there's no time to make individual appointments really.
Another ETA - we've tried to time it before also to get either Darth Maul or Asajj Ventriss, and you can kind of do that by letting people pass you. So maybe if you are really heads up you can count it out. You'd need to be between kid #90 and #120. That is not going to be easy going the rope drop through the Indiana Jones que. You might be able to ask people coming through what time they got anmethid estimate it, but seriously, unless you could only possibly be there at that one time because of your flight or something I wouldn't even try it. It would be much harder than getting a picture with Kit Fisto and Shak Ti and Anakin all at once.
One last ETA: Just honestly. Here's the thing. It is really, really good to have a plan, and it is good to have information before hand to plan, but don't overplan this. Make sure as you go you have some flexibility in your plan and options because it will be surprisingly crowded, it could be hot or rainy, your kid might be invited to be in a parade who knows. Just imho. I would count on more time than you are allotting for jta just for getting around the crowds. Remember also that you'll want to take your jta photopass card to get the pictures transferred to your regular photopass and you'll be surprised at how long that will take.
AND yeah, it looks like they are planning an 11:00 parade.