Y not do both, do the crt for breakfast the day b4 and tell them its her birthday tomorrow,,,,,,,,,,,,,,they will still bring out a cupcake and sing. The food is good, and they will bring out more food and danish (which is so good) and let you take what you dont finish to eat later as a snack.
Then on the night of her birthday do 1900 for dinner. We did both and they were both magnificent! Eating in the castle is a treat itself, but only character meals for breakfast and lunch (cinderella and co)
1900 park faire is amazing for dinner, you are greeted by the fairy godmother and she will blow pixie dust on the birthday girl...... Also Cinderella, and the Prince and Suzy and Perla are there , very magical! They bring a cupcake and a plastic placemat signed happy birthday from all the characters for the birthday child to keep. If you decide to go there, remember to try the strawberry soup!
And be sure to get a birthday pin on arrival at each park................they do give extra attention to children with the pins on, (might get to go on a ride a second time , or a free fast pass ride, etc)
you will have a great time , no matter what you decide!