Hi, Melissa!
Yes! You can certainly use your Dining Plan credits for the
Fantasmic Dining Package. Mama Melrose's and Hollywood & Vine would be one credit, and the Brown Derby would be 2 credits as this is a Signature Dining location.
I suggest you and your entire party stay together until you get to your seats. This ampitheatre is big. Did I say big? I meant huge! Once seated, your daughter might be excited to see all the guests filing in and will be fine. If not, once your hubby knows exactly where you are, he can take her get a snack or just for a quick walk.
When my kids were little, I would have my secret bag of tricks. Before leaving home I would stop by my local dollar-store and pick-up glow sticks, light up necklaces, or anything bright and shiny. These will be worth their weight in gold when waiting for shows or parades as they will keep your princess busy and save you lots of money from buying the merchandise being sold. My kids are now 10 and 13 and they still ask me if I have any glow sticks with me when they are waiting for the parades!
With your VIP seating, your wait will not be quite as long and with a bit of planning, I think your daughter might have fun waiting for the exciting Fantasmic! show. Enjoy!