I would develop a list of "must do" things. Then try to plan around those.
You will never see everything in 10 days especially with kids. We just recently saw everything and we've been 9 times. Our first trip was 14 days and we were just a couple. Didn't even get to a water park.
If you decide on those things you can't miss then you can wait in lines for those. After that you can gauge things by how long the line is and how tired the kids are. You will need at least 2 days in MK and might need more if the lines are long. You can do AK in one day. MGM you will need at least one day and probably two to see all the shows since they are now on a reduced schedule. Epcot will depend on what you want to see. Our son isn't into the World Showcase, much, so we don't spend a lot of time there. At least one day and could spend a lot more time there, too. Don't forget about Downtown Disney and the Marketplace. Also, there is the Wide World of Sports and the water parks. Lots to do here. And, if you are traveling at Christmas, looking at the resorts is pretty neat.
Must see resorts at Christmas: Grand Floridian, YC/BC, Boardwalk
We did character meals to eliminate the time we had to wait in lines to see them in the parks. It just sorta depends on what you want. Then when we see lines for autographs or pics in the park with characters we skip them. When it is busy it saves a lot of time.