Having been to WDW many times (more than I remember) as solo, adults only (either just me and my wife, or with other adult friends), with our family (3 kids) or with extended family (in laws, nephews, etc) this is my advice to you.
Strive for a balance between under and over planning.
If you go into WDW with no idea of what you want to do, you are going to be very disappointed. Unfortunately WDW has become crowded at all times, and wait times for popular rides can get very long, and many table service restaruants book to capacity well in advance. So take a look at a guide book, or a web site, or Disneys site, or the My Disney Experience app with your kids and pick out some of the stuff they really want to do. Then make Fast Pass + reservations for those rides and Dining reservations for anywhere special they may want to eat.
Then, after that, stop with the detailed planning, and just do rough planning. Don't plan out every single momement of your trip. You are not going to be able to see and/or do everything WDW has to offer. Not in one trip, not in half a dozen trips. Get comfortable with that fact, and don't try it cram it all into one visit - or you will be disappointed. Do, however, take a look at the maps of the parks ahead of time, so you at least have an idea of what attractions you want to visit and in what order. Magic Kingdom is probally the most "free flowing" of the parks. There are a number of attractions/events that only happen at specific times - such as parades or shows, but many of the attraction are just wait in line and go next type things. EPCOT and AK are in the middle - there are a bunch of "whenever you get there" attractions, but there are also some scheduled shows or events. EPCOTs are mainly performances in the various countries, and AK has some stage shows and some performance acts as well.
If you end up using one of your days at DHS, that will require a bit more planning, as many of the attractions there are at scheduled times, as they are stage shows.
However, what it really boils down to his have fun. Your kids are young, they will get distracted and see something fun and want to do it. Let them. Maybe they are on Tom Sawyers island and are loving the fort. If you whip out your shchedule and say "kids, we have to leave, because the schedule says we have to eat at Pecos Bill's in 11 minutes" it is going to make for a sad trip. Now if they are doing something that would make them late for a stage show they really wanted to see, then yes, maybe you explain to them that if they stay at the dino dig site any longer then they will miss Flights of Wonder (now we have moved to AK by the way). The best way for you to enjoy WDW is for you to enjoy your kids enjoying WDW.