My best advice is to get your kiddos involved in the planning. I'm a single mom and I think one of the rare advantages of being a single parent is that it is easier to let go and let the trip be all about the kids.
You can get the planning video from Disney and watch it with your kids. A warning, don't let them into the resort section unless you want to hear whining about the resort pools, etc.
You can also get kid-friendly guidebooks tlet them look through. Search the Travel Channel for upcoming rebroadcasts of Disney shows. Search youtube for ride videos for anything you think they might need to be prepared for...anything from Haunted Mansion to Tower of Terror is on there.
Once you've spent a month or so looking, go to the Disney site and personalize a set of maps. Those will let your kids become familiar with park layouts prior to your visit.
My boys favorites are the Buzz ride, Soarin', and Fantasmic. They are looking forward to riding Toy Story, Big Thunder Railroad, and Mission Space.
My advice if your kids aren't daredevils: take them to a local carnival before you go. Encourage them to work their way up the rides. They won't need to do the extreme ones unless they want to do the big coasters or tower, but using a carnival as a warm-up may prepare them better than just thinking about rides.
One thought: be prepared for them to balk at something and have a plan. They are old enough that you might want to either get them cheapie cell phones or walkie talkies so if one wants to wait outside a ride he/she can. Just park the kiddo somewhere in site of a CM and you'll be fine.
Also, be prepared to have to stop for street entertainment, etc. Older kids might be willing to blow by this, but I've found that my kids get as much joy out of watching this sort of thing as they do from the big rides.
Finally, my advice would be to think souvenirs out well in advance. Talk about your plan. My boys know they get to squish pennies in the parks. I will let them choose 1 shirt per park (I plan this as part of their regular summer wardrobe) and will let them get a pair of ears. They've already decided that they want their pictures taken at Star Traders, would like to build light sabres at DTD, and want to get buckets of
Lego stuff there, too. Since they know we aren't about "stuff", that is probably about all we'll come home with!
Enjoy your trip!
I would check around the boards and see what might interest you and your children. There is so much info here. 
My kids have a blast looking at the food reviews and making dining choices based on them. Seeing the pictures ahead of time helps them to try foods that they would have never tried from just the menu description.
