I got this from the wdwtoday.com website...
Guests who prefer a reserved seating area for Fantasmic can purchase one of tow viewing options. Both options have an amazing view of the show along with Dessert.
FANTASMIC DESSERT BUFFET
Prices:
* Balcony seating: $56 per person
* Premium seating: $56 per adult (10+) / $46 per person (3-9) 2 and under are free provided they sit on your lap
*subject to change
To reserve your seats, contact your
Travel Agent or call (714) 781-4400. Reservations can be made a month in advance and do book up quickly. Note that your reservation must be made on the same day the prior month. For instance, if the show is on December 10, you need to make a reservation on November 10. The Ticket office opens at 8:00AM, and you need to call right when it opens, especially to get balcony seating.You will be required to pay for this at the time of booking and tickets must be picked up on the day of the show at Guest Services, located to the left of the
Disneyland Park entrance. Be sure to get your tickets before Guest Services closes.
Fantasmic Balcony Seating
There are approximately 20 chairs available at this location and reservations include unlimited dessert and drinks. If your reservation is for the first show, you can stay in your seats and enjoy the fireworks show afterwards. Access the balcony by going up the steps to the Gallery above Pirates of the Caribbean. Seating is determined in the order that the tickets are purchased.
Fantasmic Premium Seating
Premium seating is set up along the river, in an area in front of the Haunted Mansion. There are more seats here. Dessert is served in keepsake boxes. After the first show, guests can remain to watch the fireworks. Seating is determine by first come first serve. About an hour before Fantasmic, go to the seating area with all of your tickets, and sign in with the cast member. About a half hour before the show they start seating. Everyone in your party must be there with their ticket in order for your party to be seated. If you are not there, then they'll take the next person on the list.
Heres the link for the whole page including pictures...
http://www.wdwinfo.com/disneyland-california/disneyland-fantasmic.htm#8