Hi Melissa,
It's a great idea to get a head start on your fun during Disney's Hollywood Studio's Extra Magic Hours. I am a big fan of Toy Story Midway Mania, so I think hitting it up as soon as the park opens is such a great idea. Even though the attraction does open during the morning Extra Magic Hours, as of right now, Buzz and Woody will only be available at 9am for their
Meet and Greet at Pixar Place. So, have a blast on Toy Story Midway Mania as many times as you can, and then head over to get in line to meet Buzz and Woody after. You'll still have an advantage, since you'll already be in the park and ready to go to "infinity and beyond!"
I hope this answered your question, Melissa. If you have any more questions before your vacation, please feel free to ask us at anytime.
Have a fantastical Disney day!