I would call, book the Fantasmic first and then focus on the others. The computer IMO may be more time consuming then it is really worth. By the time you log in, verify your reservation number, and begin booking, it;s just time consuming...
I tried booking online the other morning at my 180 + 10 window and after it said it verified my resort booking, a few moments later it said unable to reserve this far in advance. I then called and the CM told me it happens sometimes.....
Two computers SEEMS like a good strategy in theory, but I don't see it being THAT beneficial...
Good luck, I hope u get everything u want!