I can tell you what works for our family, but your's may be different. We just got back a couple weeks ago, 3rd full-length stay, 5th trip in total since our kids were born. Our girls are 5 and 3, so same age as your kids.
First, and most important, when is "soon"? If you're going in February, that's excellent - probably the best time of year to go, for both weather and crowds. We went over christmas break - first and last time we'll do that. The crowds were out of control. There was nothing "magical" about it. But if you're thinking March, avoid March break if possible. I was there last year at March break, and it was liveable, but if you can avoid it, do. And remember different states have the break at different times.
We've stayed at Fort Wilderness in the cabins - they're great, because you can make breakfast in the room (call a grocery delivery service ahead of time, they'll bring it right to the cabin, including beer/booze/wine, if you want) and the trip to the Magic Kingdom is not only fast, it's easy. If you're taking a stroller, you have to fold it up on any bus, but from Fort Wilderness you take a boat, and you can push the stroller right on.
edit: damn shift-enter=post.
That said, the value resorts are great for the kids. The hotels have giant statues of characters from the movies - our girls could spend their whole vacation staring at the 30-foot tall Buzz Lightyear
The pools are cool, and there are lots of food options.
Speaking of food, get the dining plan. Combined with the park passes, I don't think you can eat any cheaper, because restaurants at Disney are stupidly expensive. Plus, you're not constantly watching money being spent and keeping that running total in your mind of just how much this trip is going to end up costing. The food at Disney is actually pretty good. Not gourmet, by any means, but if you know where to look you can find some really interesting options, and lots of healthy stuff too. At the Magic Kingdon, go to the restaurant opposite the Haunted Mansion and get the hummus and coleslaw sandwich - I think it's call the Lighthouse, or the Anchor or something. It's one of the best sandwiches I've ever had.
As for parks, you'll really end up spending most of your time at the Magic Kingdom, with kids that age. Your eldest might find some fun stuff at Hollywood Studios, but if you do go there, get there before 9:30 and one of you go straight to the Toy Story ride and get fast passes. They run out usually by 10-11am. I've never actually been able to get one. The Little Mermaid and Disney Jr. shows are really fun for the kids, but that's about the end of stuff at that park for really young ones. Animal Kingdom has about the same # of fun things for kids that age. Epcot has a few more - your oldest can go on Test Track, which is really fun, and the Finding Nemo ride is cool.
Park Hopper option - depends on how much energy your kids have. We've done it both ways. It definitely has its advantages, though this last trip we didn't bother, and there was only one time where we wished we had it.
For non-park stuff, try visiting some of the pools at the other hotels. We went to the pool at the Caribbean Beach resort - it's pirate themed, and is one of the coolest pools I've ever swam in. 2 waterslides and a pirate ship water park play area thingy. And 2 other people using the pool, that's it. Of course, the temperature that day was about 8 celsius.
I'm sure I've got tons more info - shoot me a pm if you want, or just ask questions here.