First, hit the most popular rides (those that start developing a line quickest) Fantasyland starts getting busy quickly, so hit that early if you have small kids. If you have 'big kids' that want to do Splash Mountain and BTM, hit those early and grab some fast passes for later on if you want to do it again. Then head over to Space Mountain. This is assuming it's going to be moderate to busy when you're there. If it's a quiet time of the year, it won't be as important.
Somehow, it seems that the wait times for some of the Fantasyland attractions can start reaching 30 minutes by noon, even in the quiet seasons.
Have a great trip!