I look at it this way, are you going at a busy time of year? This may make your decision. If you are going at a busy time of year and don't want to stand in line to see the characters, then yes well worth the $50.00. I have seen lines in Mickey's Toontown waiting an hour or more just to see a few characters. In my opinion I would rather spend my time riding the rides and seeing the shows. For your four year old, characters are going to be a must.
I always schedule around 4 or 5 character meals, different characters generally, so my kids can see the characters, eat, and enjoy the atmosphere. I personally don't want to stand in line for an hour or more to see their favorite characters. If you have ever been to Disney in Toontown they usually have 2 or 3 lines to see the characters. One line might have Mickey, Minnie, and Goofy. After you see them you have to start at the back of the line to see the princesses, which will usually have 3 or so.
So you could spend several hours just trying to see the characters. But, it is indoors and air conditioned.
In regards to the quality of food, compared to the other Disney buffet character meals, I did not care too much for the dinner food, but loved the breakfast!
If I were you, I would schedule a breakfast in Epcot at Akershus, if you haven't already done so, to see the princesses!
Have a great time!