I took my 6,6 and 10 yr olds last year for 5 days. We had 4 character meals booked (1 lunch, 1 dinner, 2 breakfasts). Although they absolutely LOVED the character meals, autographs, etc., after the 3rd character meal, it was just overkill and I canceled the last character breakfast. So, if you have more than 4 character meals booked, esp. on the same days, you might consider some different things IMHO.
If you use the DP for your dinners--buffet or not and for a character breakfast or two--the dining plan is worth it--esp. if you are going in summer, as all character meals and buffets are $4 more. Also, kids like Whispering Canyon WL--not charcter, but very fun, for a change of pace--then we ride the boat over to Ft. Wilderness Chip and DAle meet/greet and sing-a-long. You can also use the dining plan for the FAntasmic dining package, if you want.