Ugh...I just type a huge long post and it got deleted...

Anyway, I'll start again:
I think the issue is more where you want to eat instead of to meal plan or not. Once you figure that out, you can see if the meal plans work for you.
I know you said you were planning only 2 sit downs, but there are some conveniences to sit downs, especially character meals. They are nice refuge from the heat and craziness of the parks (sometimes) and it's a really nice place to pose with characters and get signatures where they come to you, not the other way around.
Here is a list of the character meals.
MK:
Cinderella's royal table (PLATED): characters self explanatory
Crystal Palace: Winnie the Pooh
Epcot:
Garden Grill (Family style): Chip n Dale, pluto etc...
Akershus Norway Princess Meal (1/2 buffet, 1/2 plated)
AK:
Tusker House: Donald
DHS:
Hollywood and Vine: Little Einsteins
RESORTS:
Poly: Ohanas (family style): Stitch
GF: 1900 Park Fare: Princess/Mary Poppins/ Cinderella characters
Contemporary: Chef Mickeys
The nice thing about buffets is there is a lot of choices. Also at most character meals there are various activities to entertain those restless kids.
I would highly recommend ADRs for any sit down meal you are interested in.
Now for the meal plan...you have to consider your eating habits: Do you like desserts? Do you like fast, casual food- often burgers, sandwiches, pizza, and fries? Do you prefer whole meals, with appetizers, entrees and desserts? Do you like appetizers? etc... Do you prefer not to be locked into any 1 choice? Are you snackers?
There is a meal plan suitable for most eaters, except those that vary. What are you? What are your kids?
I wouldn't count on eating outside meals if you don't have a car. I doubt they will allow delivery on the property. You are staying on property right?
It seems like the QS plan is a fairly good deal (most QS meals cost ~ $15 dollars, including drink and dessert) and while most are the usual fries, burgers, and pizza, there are better more substantial options. In Epcot, anywhere in world showcase, there is tons of ethnic food. Additionally Yak and Yeti in AK has chinese food. In MK, Cosmic Rays has good roast chicken. And resort food courts are always good, and in Downtown Disney- Wolfgang Puck Express is really good too.