For a trip that short, I would just focus on MK and EPCOT. We usually spend 2 days at MK, 2 at EPCOT, 1 at DHS, and 1/2 day at AK. DD, 9, has loved EPCOT since she was 2. If your kids like Phineas and Ferb at all, they will probably love the Agent P missions throughout World Showcase. I would probably plan the 1st day at MK, 2nd day at EPCOT, and then the 3rd day assuming that you have a lot more to get done at MK, I would go back there. If you do MK and EPCOT the 1st 2 days, then you can always decide on the 3rd day to try either DHS or AK if you don't feel the need to go back to one of the other 2. Will you be going before the spring break crowds are over? If that is the case, then I would definitely focus on just a couple of parks as the lines will likely be long for everything and will slow down how much you can do in a day.
The one thing that could change this would be if there is something at DHS or AK which would be extremely important to one of the kids. For example, DD would probably not be amused if she did not get to ride Star Tours at DHS, it is one of her favorites. If one of your kids is a huge Star Wars fan, that ride might become a priority.
The good thing is that you have hoppers, so if you decide you really want to see another park enough to forego some time in the park you have picked for that day, then you can hop over and try it. Just be aware that hopping takes a lot of time and should be done sparingly. It often takes an hour, or even sometimes longer to get out of one park and into another- so there is lost time when you hop. Still if you are going on a trip that short, we would prefer the flexibility.
For us, AK is always the last choice. DD has never really been a fan. I really enjoy AK (although last fall it was full of construction walls which really detracted from the experience in my opinion) and she typically tolerates it for a while for me and then asks to leave and go back to EPCOT or MK. She likes the Safari and the Lion King show and seeing the characters, and that is about it. I believe it is because we have a very good zoo at home. I think that she has no interest in watching the same kind of animals we can see at home when she could be riding rides and seeing Disney characters. If you don't have a great zoo at home, your kids might feel differently about AK. AK is more than a zoo, but DD just never seemed to think it was enough more to warrant the expense of her "Disney time". I will say though that since they started doing the Wilderness Explorer booklets where you go through the park doing tasks and earning sticker badges when she was age 7, she has enjoyed AK quite a bit more, and will stay longer than she used to. I'm not sure how that will impact the next trip because she now has completely finished the book (in 2 trips). I don't know if she will want to start over, will still enjoy AK, or if she will revert to her old ways and be begging to leave by noon. I'm also not sure what shape or differences there will be at AK by your trip with all the construction.
Have fun planning!