Hi Holly,
The answer to your question really depends on how much you are likely to eat during your stay.
Personally, my family love the Disney Dining Plan and have always found that it has saved us money but that said, it certainly isn't the case for everyone.
To get an idea of what the cost of Table-Service & Quick-Service meals will be if you pay out of pocket, I would recommend that you
have a look at the menus section on the unofficial website Allears.net.
If you then consider how many of each type of meal you are likely to have per day and times this by the average amount of those meals based on the menus found on Allears.net, it should give you a rough idea of what you are likely to spend on food throughout your visit.
I would then suggest comparing this against the cost of adding a Quick-Service Dining Plan or Disney Dining Plan to your vacation package.
My now 9-year old Sons favourite
Character Meals include:-
Ohana's Best Friends Breakfast with Lilo & Stitch at Disney's Polynesian Resort
Chef Mickey's at Disney's Contemporary Resort
Donald's Safari Breakfast at Tusker House in Disney's Animal Kingdom
As your Son is only 4-years old, he may also enjoy
Hollywood & Vine at Disney's Hollywood Studios which features characters from Disney Junior.
Wishing you a magical trip filled with memories which will last a lifetime!