Welcome back!
We were recently asked for any tips for Magic Kingdom when traveling with younger kids. Sounded like a good blog post! 
Go Early
Most kids are up early, anyway, so get out of bed and get to the parks! Most people will make their way to the Magic Kingdom at their own leisure. Of course, there are the hard core travelers that will make it to the opening, but generally, this is a less crowded time to be at the Magic Kingdom.
The one exception to this rule is Extra Magic Hours. If the Extra Magic Hours occur at Magic Kingdom in the morning, this will likely be the most crowded park of the day.
Go Directly To Fantasyland
Fantasyland will be the most popular area for young children, so get here first. The majority of guests will go to Tomorrowland or Frontierland first, putting off Fantasyland for later. Later will be packed!
Part of this strategy involves avoiding characters. Characters will populate Main Street and the area in front of the castle as a distraction -- don't fall for it! It's very tempting, but as we've talked about, before you must have a plan and work your plan. The characters will be available for pictures throughout the day. Come back to them after visiting the most popular rides in Fantasyland.
Use FastPass
Use FastPass to it's maximum efficiency. To do this, when you get to Fantasyland (after going directly to it) get a FastPass for a ride in Fantasyland. While waiting for your return time, ride one of the non-FastPass rides in Fantasyland. Repeat.
Use the Train
The train that encircles the Magic Kingdom often has little or no wait and kids LOVE IT! It also helps with reducing the amount you have to walk. Stops in Toon Town, Main Street, and Frontier Land. After Fantasyland, you will likely end up in Mickey's Toontown Fair. Play around here a bit and then catch a ride on the Walt Disney World railroad.
These are just a few tips for maximizing fun and time at the Magic Kingdom with your little ones. We have a lot more in our Pre-Schooler's Guide for all of Disney World. If you just follow the tips from this post for the Magic Kingdom, you will likely ride all the rides your little ones want to ride and avoid lots of standing around in lines -- one of the most difficult times at Magic Kingdom with small children. You'll have the magical Disney vacation people often dream of, but seldom get.