Hi Jaime!
No age is too young for a Little Princess to dine with her fellow Princesses! ;)
You will definitely find children of all ages at Character Meals throughout the day, all around Walt Disney World.
When my own Princess was very young, I found that early in the day was the best time to enjoy character dining; before she was too worn out from a long, exciting day in the parks! My favourite option to enjoy dining with Princesses, while keeping a little Princess happy, is a Princess Breakfast.
If you have a Park Hopper option on your ticket, or are planning to visit Epcot theme park during your stay, I so very highly recommend
Akershus Royal Banquet Hall for Princess Storybook Dining. Breakfast, lunch or dinner are all available at this location and an advance dining reservation is absolutely necessary. Personally, I prefer the breakfast offering here as far as a 'menu pleasing to all tastes' goes! Your little Princess will be visited at the table by MANY Disney Princesses while you dine. Your meal is delivered 'family-style' to the table, making this a very relaxing dining option. The per person price also includes a complimentary photo package per group of four.
If you are using a Disney Dining Plan during your stay, you'll find that this fantastic meal option is just 1 Table Service Credit, or a moderately priced meal if paying outright.
Wishing you a simply Magical time at Walt Disney World with your pint-sized Princess Jaime!
Kirsten