Hi Gina,
Welcome back to the Disney Parks Moms Panel!
Based on the latest information I've been able to find, when Magic Kingdom Park has morning
Extra Magic Hours, the
Magic Kingdom Welcome Show will take place prior to the Park's Extra Magic Hours opening time. This means that, on a morning when Magic Kingdom Park opens at 8:00 am, the Show should start at approximately 7:40 am.
Please note however that, like other entertainment offerings in Walt Disney World Resort's Theme Parks, this is subject to change at any time. In fact, I seem to remember a time when the Magic Kingdom Welcome Show would only take place when the Park was officially open to all Guests. I've also heard that the Show can be shortened or changed slightly when it is performed during morning Extra Magic Hours. Make sure to check the time listed on the page I've linked to above as you get closer to your vacation dates.
If you really want to see the Magic Kingdom Welcome Show (which I definitely recommend seeing at least once!), I would set aside two mornings for visiting Magic Kingdom Park, one with, and one without Extra Magic Hours in order to make sure that you don't miss it. While this may cost you a few extra minutes of sleep, it's really worth getting to the Parks early from a touring perspective... and you'll be able to make up for that lack of sleep by doing so many morning attractions that you can easily head back to your Walt Disney World Resort for a nap, something that I highly recommend while on vacation!
Have a Magical Day,
Lynne