Please don't stress yourself out! DLR is typically quite a relaxed kind of place, especially in times like February when crowds shouldn't be too much of an issue. There are a few things you need to plan. As we've already said, you'll probably want to book your princess makeovers and character dining ASAP. If you want to do any night time shows, you'll need to figure out which nights to see them. If one of those is World of Colour, you'll need to pick up a FP sometime during the day. If you want to meet Anna and Elsa, or ride Radiator Springs Racers, you'll need to prioritise getting your FP. Other than that, just do what you or the kids feel like!
As a PP said, those people who plan every second of every day are often the ones who just race from one attraction to the next, trying to tick off as many as possible. They are often disappointed with their experience because they found it stressful, the kids didn't cope well, and they may very well have missed out on a lot of magical experiences just because they were in too much of a hurry to notice. Don't be one of those people. If your kids want to spend an hour playing in the splash zone, don't hurry them along because you're missing out on 'rides'.
I personally love rollercoasters, but my mum is the most timid ride person out there, and is generally the 'bag minder' at our local amusement parks because there aren't many rides that she can tolerate that aren't too kiddy. That's not the case at DLR. Yes, the dark rides are based on Disney movies, but they're great fun. It's all in the detail. I highly recommend you ride Alice in Wonderland now that it's had its makeover. The other dark rides are fun too - Peter Pan, Mr Toad, Snow White and Pinocchio. Peter Pan does tend to get a long line though and is one that's best to ride straight at opening. The Haunted Mansion is a good non-thrill ride for adults, as is Pirates. There are 2 very small drops in Pirates, but if my mum can handle it, seriously anyone can. She didn't enjoy the drops, but said it was worth going through for the rest of the ride.
I would go in with an opening plan each day (you will want to do rope drop at least once for each park). In DCA, make sure you pick a day that doesn't have early entry for hotel guests. Plan to ride Toy Story Mania first, and any other attractions you're interested in in the area (Mickey's Fun Wheel is a good one for timid adults, just make sure you're in line for the stationary cabins!). The Little Mermaid is a good one too, that everyone can enjoy. Then head over to get your RSR FPs. From there, just do what you feel like for the rest of the day. If you're a fan of the Muppets, make sure you check out the 3D movie. Definitely see Aladdin. It's not just a kids show, it's a Broadway quality full musical (just a little shorter than you'd see on Broadway) with plenty to entertain adults as well as kids. The kids might enjoy a Bug's Land and the Redwood Creek Challenge Trail. Take the Red Trolley.
In DL, you can use your Magic Morning early entry if it fits in with your plans, otherwise go on a non early entry day. Plan to ride Peter Pan first, then get your FPs for Anna and Elsa (if you want to meet them). Having said that, the Anna and Elsa situation is always changing, so make sure you keep up with the latest there. Then, again just do what you like. If you're interested in history, Great Moments with Mr Lincoln is a more adult oriented show. Also check out the flag retreat ceremony if that's your thing. My dad loved it and saw it at least 3 times during our stay.
On the third day, plan to get your princess makeovers done first thing in the morning, then head over to your character lunch in your princess dresses. Pack some t-shirts and shorts for the kids in a day pack, and you can all decide after the lunch whether you want to change or not. You might find that they're comfortable enough in the dresses as long as they have comfortable shoes on.
If you have a 4th day, you can use that opportunity to have a more relaxed start to the day, do some things you've missed, repeat some favourites, and just soak in the atmosphere one last time. The more days you have there, the more relaxed you can be while still fitting in a lot of things.
I see it a lot on these boards for parents to get their kids involved in planning the trip, picking their must-do rides etc. I would use caution doing this. Make sure you explain that although you will try to do that ride, there is no guarantee that it will be available on your trip. Part of me feels that they would be better off not knowing so there's no disappointment if they're unable to ride it for any reason. But each to their own. Showing them
youtube videos is a good way to find out if a ride might be too scary for them etc.