Welcome to Dis!
I suggest doing a little bit of research. This site, allearsnet, and Unoffical Guide are great resources. I don't recommend going all commando - just get an idea of what you want to do.
Make some ADRs. Table service restaurants are a great way to get away from the crowds. The resources listed above are also great places to find restaurants you'd like to dine at. Depending on the ages of your children, you might consider booking a character meal. You can make ADRs up to 90 days in advance, and the further in advance you make them, the better chance you have of getting what you want.
Plan to rest. Don't try to do it all. When you're getting tired, hot, and cranky, head back to the resort to take a nap and swim. You don't want to tire yourself out too early in the vacation.
Take advantage of early EMH at MK. You can do so much more in the first hour than you can in the last three. If you're going to do EMH, early MK is the way to go. (AK emh is a waste - avoid AK on early emh days)
And of course.... have fun! It's your first time at WDW! Feel free to act like a kid. Try new things. This is a vacation you'll remember for life.