If the 10 yo likes the princesses, definitely try for breakfast in the Castle. We found the food to be very good there, and eating in the Castle is a fun experience.
Chef Mickeys at the Contemporary is one of our favorites. Characters usually consist of Mickey, Pluto, Goofy, Chip, Dale, and Minnie. This is our favorite character breakfast as the food is delicious and there is a great variety.
If you prefer Pooh Characters, Crystal Palace might be a good choice for your party.
Like wdwgoofeee said, there are numerous character meals. The ones I mentioned are just some of the more popular ones.
*Edited to add, I just realized you said you will be there in March. If thats the case you are inside the 90 day window for booking PSs. I would suggest calling Disney Dining and trying to get a PS asap. Some of the character meals(especially breakfast in the castle) may be booked up by now. Good luck!