The most important thing is to know ahead of time is what appeals to you and your family. The Unofficial Guidebook (in my opinion) is the best resource. It talks about ever single ride/attraction in all of Disney.
The thing is, you can ask around, "What was your favorite?," or "What should we not miss," and get a million different answers. You know if your family will find something "boring," that someone else would find "classic," or you would find it "entertaining," and another family would say, "way too educational."
So, educate yourself. Yep, it takes time. The book is thick and you'll find yourself walking around with it. Highlight your favorite things. Use the suggested touring guides, and then CHANGE them to work for you and your family.
If family is interested poll them. Unfortunately many times family is not interested until they are ON the plane and then "Oh my gosh what do we get to see and do?" That's when you fill them in with your plans.
You have to have a plan. Plans can change. You do NOT want to spend any time standing and looking at a park map saying, "What should we do next?" You need to have a list of go here, then here, then here. Of course you can change at any time, but you need a place to start. You don't want to waste time standing still and contemplating. The time to do that is now, in your comfy easy chair.
Entering the parks at rope drop is extremely important for efficient touring. You will see so much and do so much in those first two hours your head will spin. Get them all up. It's important. Then start watching the crew. Are people getting crabby? Then it's time to sit down and take a break.
When our 14 year old announced at Animal Kingdom, "Have we seen everything we need to?" we knew it was time to sit down and have some nice cold drinks and a snack. Then we were refreshed and were able to finish up the day.
Some of your favorite moments will be at the pool sitting around with drinks while the kids play. Be ready for that.
You do NOT need a ton of character meals. A couple are more than enough. You do NOT need to go out for dinner every night. Dinner can be pizza some nights, or another fast food. Eat breakfast at your rental place. It saves money and time. Lunch is a glorious time to treat yourself to a fancy sit down meal. Everyone loves to get off their feet and rest in the air conditioning. It gives you energy.
Break up the shopping. Some love to shop. Others hate it. Let the shoppers shop, and let the others do whatever. Consider leaving the non-shoppers at the pool. Do not fill up "touring" time with shopping. Shopping is shopping, and can be done at any time. Touring is, well, seeing as much as you can at a comfortable pace for the group.
No matter what you do you cannot see it all. There is sooooo much to see and do and eat. You will all have an absolutely wonderful time. Be sure to pick up the park guides at every park. We had a delightful time with "Push" the talking garbage can at MK. Our 14 year old decided to seek him out.
The different "acts" in Epcot are delightful. The candy lady in Japan is soooo cool.
Try not to bog down your schedule with too many dinner reservations. Often at the end of a long day all you want is to relax in the pool, and not have to get all dressed up to "rush rush" off to dinner.