well, with kids as young as yours, sometimes you have to pack the whole house!
I've found as mine got older (first trip they were 21 months and 3yo, now they're 6yo and 7yo), I pack less and less. Last trip I decided i'm even going to 'splurge' and buy toiletries from the gift shop at the resort (toothpastes, etc). They have everything there and we just don't need as much stuff anymore. So it's a little more money than
walmart - but it won't break the bank for the little i need to buy, and i don't need to remember everything from home, something that becomes stressful for me.
I've also found I would always overpack, never touch more than half our stuff, but had it there 'just in case'... not worth it to me anymore. I remember our first trip, we drove, so we were able to bring anything, and we brought everything! We had a huge box full of snacks for the kids... little kids are picky and I was afraid I wouldn't be able to find snacks they'd like there. Now looking back, I could have found plenty there they'd eat.
Now we fly, each only bring a carry-on (I do laundry there - I hate tons of smelly, dirty clothes), and I'm much less stressed when we travel. I also always plan on buying each person a WDW t-shirt or sweatjacket, so I even factor that into the packing. less is more for me now, but again, yours are little, so bring what you know will make them comfortable.