<font color=navy>You have a couple of options.
You can spend about $47 or $49 to sit up in the balcony section & have some refreshment while you watch the show, orrrr,
You can stake out a spot on the Riverbelle Terrace at around 5pm - these seats go quickly, and by 5:30 the terrace is usually full for the 9pm showing of Fantasmic. You can take turns saving a table while the other parent takes the kids on attractions. You can eat at that time, or later, and you can either have something off of that menu, and/or grab a burger from the Stagedoor Cafe right next door.
We've done this quite a few times, especially w/guests from out-of-town, or guests who've never seen the show.
If you opt to do this, get there early and try for a seat along the railing (corner next to the brick wall is the best). I've sat at an interior show, and had a father stand his child up on the chair, blocking our view the entire time - so I make sure to get the front (and save a couple of extra seats for children I see below who can't see the show & invite them to sit w/us).
If you'd rather spend your time having fun with the family, you might try for a decent spot on the ground by 6:30 or 7pm.
Since we've been so often, I don't mind sitting & holding the spot. I usually take a book, but normally end up talking to the people waiting next to me.
