An example and some more comments will be added shortly.
Example assuming park hoppers and staying on-site: 2/17: Rise early, have a quick breakfast in room or at hotel restaurant, and be at Animal Kingdom by about 7:30 am. You can pass security and the turnstiles will probably open well before the official opening time, which according to the official calendar today is 8 am. Use the bathroom if you have to, visit guest services, get a locker if you want, etc., depending on your needs. You can view the natural habitat zoological exhibits in the transitional area called the Oasis, and you'll be held at the end of that by a rope barrier until official opening.
When the rope drops, tour around and see as much as you can see before it gets too crowded. Have a plan in mind of what you want to see. The Official Guide to WDW has good ideas.
You might want to grab an early lunch before it gets too crowded. If it's not too hot (and it shouldn't be in Feb) (because dining is all outside here), Flame Tree opens pretty early (usually opens at 10 am when high crowds are expected). One strategy is to wait until the attractions become too crowded, of if you have to wait a bit for a fast pass time, try to go then. If lines are too long there, wait until the next step to eat. Grab a pretzel somewhere or something to tide you over.
If and when it gets so crowded that you can't stand it, or if you've seen enough for today (remember you can come back on another day if you have hoppers). This may happen as early as noon, maybe even 11, depending on the day, and your tolerance for crowds. Go back to the resort, hit the pool, eat lunch at the counter service restaurant there if you haven't eaten at AK, take a nap, visit the game room, or just hang out. Maybe you'll want to tour another resort or two that are not yours. We like to do that.
Definitely rest, or maybe even sleep a bit.
Now you have many options for the afternoon/evening. Here are 3. Which you choose depends on many things, including what time you quit AK.
(1) Go to Epcot. Plan to arrive between 3 and 6. If you arrive closer to 3, check out the FP and attraction wait times by checking the sign boards. Last time I was there, the central board had only wait times, whereas the East and West boards had FP times, too. I don't know why this is. But don't get your hopes up. You can always do the Future World attractions on a day you go to Epcot early in the morning. But it doesn't hurt to check. If you arrive closer to 6, FP will probably be done, but some wait times might be down. You never know.
Mainly on an afternoon visit to Epcot, you want to be visiting World Showcase. Stroll around and shop. You may be able to do the water rides at Mexico or Norway. Get something to eat. The Biergarten has a large capacity and is almost always available. Watch Illuminations and head home.
(2) Late night MK. This option almost requires a sleep in the afternoon, especially if you have youger kids.
After sleeping, grab a quick bite and head for the MK. Plan to arrive at about 8-9 pm. It will be VERY crowded, and people will be queueing up for Wishes at 10. Wishes is a great show no matter where you see it from, although it is best if viewed from the end of Main st nearest the castle up to the castle itself. I personally like to try for the bridge to Tomorrowland. You may have to go on the path that goes past the Plaza restaurant and the Tomorrowland Noodle Station to get to it more easily, though. If you get stuck somewhere, don't worry. After Wishes a lot of people will be clearing out.
Try to get EMH wrist bands before the rush. They used to do this all through the park, but it changes from time to time. Ask a CM. I don't know when they start giving them out.
The reason I like to watch Wishes from the Tomorrowland bridge on crowded days is that after wished tons of people will leave the park, and if you're over by main st, it will be VERY difficult to go the opposite way towards the castle.
After Wishes, or if you are not interested in Wishes, during Wishes, check out the attraction situation. It should be getting pretty good now even on crowded days. Grab a FP if it makes sense.
There will be a spectro parade at 11. If you're interested, go look. Again, I think the best place is the Tomorrowland bridge, but go whereever. Again, if you're not interested, see what the attraction time are. Should be getting even better now.
When Spectro begins, they will start blocking people from crossing the bridges into the lands from the hub unless you have a wristband. Now you've got three hours to spend in the park with other resort guests only. Even on crowded days, it's quite pleasant. Tour until 2 am, then go back to the room and collapse.
If you have no interest at all in Wishes or Spectro (or at least today), then you can either try to see attractions when most everyone else is viewing these things, or plan to arrive around 10-11 pm.
(3) Go to Epcot, as above, and then if you have the energy, hit the MK EMH. I've done something like this before, but it is a long, long day. Take the next morning off.
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Now this is just an example, and granted it is an extreme example, but the principles for any given day is the same: Use park hopper if possible. Go at park opening, take a break, go to another park (or the same park) a few hours before closing. And use FP wisely. Sometimes you'll want to skip the beginning or the end of the day. Sometimes taking a break means staying at the park, but just hanging out somewhere and not trying to fight the crowds. It's all up to your family's personality.
