Hi Gina,
I can't think of a more magical place on earth to celebrate a birthday! Start it off right by visiting a Guest Relations location to pick up "Happy Birthday" & "1st Visit" buttons for your DDs. If you're going to MK, stop by the Harmony Barbershop in Town Square for some fun colored hair gel & sprinkles (this is less expensive than BBB but still adds a little pixie dust to your day). They will get lots of birthday wishes during the day.
If you are planning to eat at a family table service location you could get a mini cake in a special Disney Princess Jewelry Box for your daughters which includes a special surprise toy. These cakes aren't that expensive & available at most Family table service locations. Call 407-WDW-DINE for more info.
You could add more pixie dust to their BD dinner with party favors. Options include a goodie bag with a Mickey party hat, game, coloring book & crayons. The deluxe goodie bag contains all of the aforementioned plus a magnet activity set, Mickey shaped straw all in a special celebration tote bag. These are available at most Family table service locations. Call 407-WDW-DINE for more info.
The
Disney Florist & Gift Department has a lot of great idea & gifts to fit every budget for BD celebrations. Visit them online or call 407-827-3505.
I know that you didn't ask this but I recently answered a question for money saving tips on food that may help you - click
here for more info. Wishing you & daughters many magical memories on the first trip :-)