Hi Kristin!
I always make Advanced Dining Reservations (ADRs) for two princess meals while we are at Walt Disney World. We typically do Cinderella's Royal Table (CRT) on the first day of our vacation and then Princess Storybook Dining at
Akershus Royal Banquet Hall later in the week.
Since you have three girls, I particularly think that two princess dining experiences is perfect. Your son will get a sword at CRT and will receive special attention from the princesses, so he won't feel left out.
1900 Park Fare has an awesome Cinderella's Happily Ever After Dinner and I think it is definitely something that your little princesses will love. They will get to meet Cinderella and Prince Charming. Prince Charming isn't at CRT, so this will be a new experience.
Another fun character dining experience is Chef Mickey's, your kids will all love that. You may also want to make an ADR for 'Ohana and they can eat with Lilo and Stich at breakfast.
I hope you have a magical vacation! Please let me know if I can help you with anything else!
Magically,
Stacy