Plan, and plan and plan again before you get there. View the websites for times, etc. and map out what you what to see. Get the kids involved with choices ahead of time including any shows. We have a rule of taking turns for choices but you must be flexible and if the ride is over a 45 minute wait you have to be willing to skip it. If you do this ahead of time, it saves lots of time from discussing it at the parks. It's not fun to do this at the parks and leads to arguments, etc. Have it all understood before you go. Absolutely, do priority seating, if you are doing the sit-down restaurants in the parks or the resorts. Try not to go back and forth too much with resorts and parks; it wastes too much time. We are breakfast and late lunch people at this time of year. You can do breakfast before park hours; so, you can use that valuable time to enjoy the parks. If you must have a dinner then I would wait until late when you are done with the parks for the day.
As soon as you can, get into a park! I prefer the early entry park. Early entry is a matter of choice but that first hour is golden because everyone doesn't get the privelege, nor does everyone get up that early. Go to the farthest point in the park of what you plan on seeing, especially if you don't do early entry, and then work your way back towards the front. Avoid at all costs to do any back tracking----big mistake. Towards late morning, early afternoon consider park hopping, if it's getting too crowded at your current park. Take a nap, if the kids need it in the afternoon, and go to the later parks at night.
MK and Epcot stay open pretty late at that time of the year; so, it's real fine to pick those parks for the evening. We've gone as far as skipping those parks in the morning and only seeing them at night. Park hopping is a real plus at this time of year. I strive towards more hours at the park; so, go early, take a nap and stay late. This needs to be understood ahead of time with kids, too. We all know they fight naps and then are very crabby later in the evening. I would make it very appealing to them to follow this course of action.
If you plan your course of rides and attractions ahead, you will be quite suprise how much you can accomplish even though it's the busy time of the year. We just about always get what we want done. Stay flexible! If the lines are very bad on a prime ride you've chosen to do, you may have to skip it or choose two rides instead that are not crowded. This is were it gets hard because this will be someone's pick and they will feel cheated if you switch plans but if you stay stubborn about this then you will not accomplish as much. It's a hard choice, here. If you are in the same section of the park, you may be able to try the crowded ride again and it won't be as busy after you've done other rides in that area. You can also break for a meal in this area and try afterwards to see if the ride has lessen in the wait department.
By all means ride the attractions during parades, fireworks, etc. if you can skip those features. It's the best time to do the prime rides. This is why planning becomes important.
We don't go at it commando style but we are forging ahead all the time. I do skip enjoying some of the resort perks at this time of year, like swimming, if we are behind in our plans.
Recent reports have shown a climb of 33% this year over last year's attendance; this could mean you will be in for a rough time. Even with the recent bad weather, numbers are up for the parks. This means you will probably have to be very flexible to get the most out of your trip.
Have fun. Even if everything doesn't work perfect, you are still at WDW!