Hi, Jocelyn!
Booking the
Fantasmic! Dining Package is a wonderful way to avoid the super long stand-by line. With the package, you get a voucher for VIP seating with a separate entrance. And really, who does not like a little VIP treatment!
If you choose to switch your reservation, Hollywood & Vine is only included for the Package at dinner. For lunch, you would need to choose the Brown Derby or Mama Melrose's. Please note that the Disney Junior Pals will not be at Hollywood & Vine for dinner, so you might want to keep your breakfast reservation if you want to meet them.
What I would probably do is keep the breakfast reservation, have a snack for a light lunch, then plan an early dinner at Mama Melrose's. This way, you get to do it all!
If you choose to skip the Fantasmic! Dining Package, plan to be in stand-by line one hour prior to showtime. Bring some snacks and glow sticks to keep your little ones busy, and stay together as the crowds for this nighttime spectacular get very large. Whatever you decide, have a great day and magical night at Disney's Hollywood Studios.