What two days are you there? Are you doing a magic morning? If you are going to be at DL for a magic morning (getting there by 6:45/7am), then do DL on that day. You'll be able to cover most of Fantasyland and Tomorrowland easily. However, if you're not going to show up until 8am, do DL on the non MM day. It's more crowded on the MM day.
Start collecting FP for the big rides early on - you go to a machine, stick each park pass in, and you get a ticket (FP) for each one. If you have 4 park passes, you can get 4 tickets. There are 3 different times on the ticket, but only two you need to consider. One is the return time for the ride. It will say something like "return between 9:30 and 10:30." Forget the 10:30 - it's irrelevant. This means that you can use that FP to get on the ride anytime after 9:30. Then look underneath, and in smaller print it will say something like "you can get your next fastpass after 9:30." This means that regardless of whether you have used your first fp or not, you can go get another set after that time. In the mornings it's generally about an hour later, but as it gets more crowded it can be up to 2 hours. Before the park opens at 8 you can get FP for space mountain and buzz, but buzz was a walkon for us until at least 10am, so unless your kids are huge fans and want to ride a lot, I wouldn't bother with the FP. I personally think the ride is overrated but my kids love it.
Then head to Frontier/Adventureland - get Indy FP first (their return time gets really late, fast), then Splash (ride Pooh while you're over there), then Big Thunder. If you work quickly, you'll find you will probably be able to double up on many of these fastpasses. Plus, if you use the tickets for the little ones to get FP for the big rides, the older kids can go on twice using their tickets.
Do the other day at DCA, or half and half depending on how tired you all are. Get WOC FP first thing (or just buy the picnic and skip the big line). If you're there early (DL hotel guest), you can get on soaring right away. However, I recommend grabbing a FP for soaring and then heading over to TSMM - the lines will be really long the rest of the day. The first Aladdin show is around 1:30. Bugs Land you can do anytime - it's not crowded. A kid older than 5 will be pretty bored, and you will be done in under 1/2 hour. You could even head back over to DL for the afternoon/evening and then back to DCA for WOC if you want.
You kind of have to play it by ear based on crowd levels and kid fatigue, but that would be my general strategy.