We are there the week after you (12th-20th)! We are going to Harry Potter one day as well. I think the week you are there is pretty low crowds as well (3’s and 4’s mainly). I am getting ours through undercover tourist and your post made me realize I hadn’t ordered them yet! Going to do that now!
We got our disney tickets through this site and they had very fast shipping. Since you are going in the next week though, you may need to see about picking them up in orlando - that is an option with undercover tourist - or just buy at the gate or at your hotel.