We have thought about leaving DHS for dinner because EPCOT, BC/YC (where we stay) and Boardwalk are all in the area. But with three kids (and we also have three kids) we find it much easier to stay at DHS and reduce travel time.
We really like Mama Melrose and Brown Derby. If you go early enough (and are not on the dining plan using 2 TS credits) we think Brown Derby can be a good option for kids. The kids' menu is good, and if you get a table by the window, they can see the Sorcerer's Hat and all the traffic outside. Since one of our three kids is a pre-schooler, we don't order multiple courses there and we're out in about an hour. (Although our pre-schooler was doing great for our lunch there in March, so we had time for grapefruit cake!)
Mama Melrose is also a great kid-friendly option - we like the food and the atmosphere. And we always stop to see Lightning McQueen down the street before (and sometimes after) dinner!
We have tried the Sci Fi for both lunch and dinner, and prefer lunch. Although some have mentioned that you can still order burgers for dinner, even though they are not on the dinner menu. That's what we would do if we went back. It's a fun place to try at least once, but our boys don't care for the old movies, and it's tough to seat a family of five in the cars. (We sit with our older boys in the front row and my husband and I share our seat with our pre-schooler.) We also can't really talk to the kids with that seating arrangement. But again, it's very fun to try at least once!