We've just come back from a 3 week trip there over Easter and it was incredible, although very busy by the end of it.
I second the dibb website, it's great for advice and tips.
A few things that really helped us was
Rope drop the parks, so get there before they open, if your staying onsite you can get in 30mins before offsite guests, the bad news is the queues start building about 1hr before the early opening, so if early opening is 8.30am, to rope drop you need to be at the park for about 7.30am. Usually by about 10.30/11 the queues are anywhere between 1-3 hours, so those early couple of hours you can usually do about 5-6 rides with little to no queue.
It was so hot, even though it was only 34 most days humidity was around 90% most days so by lunchtime it was so hot and uncomfortable to walk around in, you can combat this by taking fans/water cooling sprays with you, if you buy in the parks they cost $22 each!
Some people had umbrellas which were a good idea and also cooling towels that you can wet under the water fountains and put round your necks.
Don't try and do it all, we did early mornings and after went back to the hotel for a swim in the afternoon, we tended to have early nights and the youngest would've struggled with late nights and early mornings. The one day we had a lie in was a waste for us as by the time we got to the parks the shortest queue was 140 minutes.
Food and drink is really expensive but the Disney hotels have a fridge so we got an Uber to Walmart and stocked up on breakfast items, bottled drinks, milk cheese etc.. we took food sandwiches crisps etc.. into the parks and saved an absolute fortune.
The only real negative I would say is the heat, everyone is affected by it and young kids seemed to really struggle with it we saw lots of tears and tantrums, we even joked that Disney is responsible for a huge amount of divorces! But with planning you can deal with most of those issues. Just do your research.
Have a great time, your kids will love it!