The most important thing while planning for a vacation with the kids is that it should make everybody happy including the kids.

The first thing to decide is the number of days you will be on vacation. And that depends on the budget you have set.
The next important thing that you have to decide is what you are going to do during those days. You may think of taking your kids to a National Park, an amusement park, a children's show depending on what is available.
There are some great resorts in almost all places where there is something for the entire family.
Also you can think of the Disney. There are special packages to Disney from throughout the world.
Else, you can go for a long ride with your family and do the hotel reservations and plan something that you can do there. Choose a hotel that is spacious and have enough facilities for the children to have a good time.
Once, you have decided on the destination, make a list of the things you are going to need including the favorite toys of the kids and pack lots of food and drinks. Think of something creative to keep the kids busy.