Please read some guide books. Walt Disney World is huge and even in your 2 week trip, you won't get to see and do everything.
Plan on arriving at each park at park opening. You want to stay ahead of the crowds. Have an idea as to which rides are important to you and use fastpass whenever possible. (Just use to park ticket to obtain a pass).
MK - your 4 year old will probably want to ride Dumbo. Head there first as well as all rides in Fantasyland. If your 7 yr old wants to see the fairies, you need to get there at opening (10am I think). Don't miss Wishes, the fireworks show at night, just beautiful.
HS - Toy Story is the big ride here that your kids will love. Head straight there, grab fastpass and then get in line, this will assure you 2 rides that day. Fantasmic is the night time show, not to be missed. Arrive at the theater at least an hour early (you can buy food in the theater to snack on while waiting)
Epcot - Test Track will be fun for your family. The World Showcase is lovely to walk around. Make sure to hit the Kidcot stations where the kids can make a mask and get a charm from each country (free to do) or for $6-7 you can buy a passport that they can have stamped in each country. Kim Possible missions will be fun for them to do while in the World Showcase. Illuminations it the night time fireworks show here. Stake out a good spot along the water about 45 min. before the show.
AK - If they are somewhat daring, Expedition Everest is a fun rollercoaster. Everyone heads there first, but if you jump in line, it's usually a 5-10 min wait. The safari is a must see and if it's not cold, the kids will like Kali Rapids ( you will get wet). They have a fun parade, but no nighttime fireworks. Park usually closes around 5
Either waterpark is great and you can spend the whole day there (they also close around 5).
As others have said, if you don't have any dining reservations, call now. I'm sure your choices will be limited. You can eat at any counter service place in the parks, just can't have a table service without an advanced reservation.
Be prepared for expensive prices. A bottle of water or an ice cream will cost $2.50-3.00 each. A counter service meal is about $8.00. Portions are big and could be shared and if you want to save some money, order water instead of soda. Bring some crystal light packs (or propel) some people think the water tastes funny.
Have a great trip.....WDW is awesome!!