Special care is needed whenever you are plannning a vacation with young children.  Rest assured Disney World may be one of the best places to vacation with your young children.  The Disney Parks and Resorts are set up to accomodate families with young children and help them have a magical Disney experience.

How Old Should Children Be To Visit Disney World?
Determining how old your children should be when you visit Disney World is really up to you.  If you are looking for your child to enjoy the trip, I would recommend a time shortly before their 3rd birthday.  There is nothing wrong with children younger than that, but there are a lot of benefits before the child turns 3.

Children under the age of 3 receive free admission to the Disney World theme parks.  They are not required to participate on the Disney Dining Plan if you purchase it for your family and you can either purchase food for them separately, or they can share your food.

From a cost benefit taking the trip just before the child's 3rd birthday allows them to be old enough to get more enjoyment out of the surroundings and yet they do not add hundreds of dollars to the cost of the vacation.

Disney World Theme Park Benefits
When traveling with young children there are several Disney Recommended Theme Park benefits that you should take advantage of in order to make your day go smoother:
•Rider Swap option is available at select Disney Theme Park attractions. Rider Swap is when Guests take turns waiting with youngsters too small to ride a certain attraction, then "swap" with another adult Guest from their party to experience the ride without standing in line twice. See a Cast Member at the attraction for additional information.
•Baby Care Centers, hosted by Nestle Good Start, where you can change and feed your baby can be found in Disney Theme Parks. Guest Services at Magic Kingdom theme park lists Baby Care Center locations at Magic Kingdom theme park, or look for the pacifier symbol on each Disney Theme Park Guidemap, available at the Park entrance.
•Disney′s FASTPASS reservation system, which reduces time spent in line, is available at select Disney Theme Park attractions. The following "Fun for Little Ones" attractions use Disney's FASTPASS system:

Magic Kingdom Theme Park
  Buzz Lightyear′s Space Ranger Spin
  Mickey′s PhilharMagic
  Peter Pan′s Flight
  The Many Adventures of Winnie the Pooh

Disney′s Hollywood Studios Theme Park
  Voyage of the Little Mermaid
  Toy Story Mania!

Disney′s Animal Kingdom Theme Park
  Kilimanjaro Safaris

Stroller Options
Although Disney also offers stroller rental, I would HIGHLY recommend purchasing an inexpensive umbrella stroller that folds easily for your trip to Disney World.  Not only will you save A LOT OF MONEY from renting strollers, but they are much easier to navigate and get on and off of Disney Transportation.

Even children who are too old to ever use a stroller at home will benefit from having one at Disney World with the large amount of walking that occurs in a typical Disney World day.  For the small investment, you will be glad that you brought one along.

Disney World Resort Benefits
Disney Resort hotels, designed with little ones in mind, offer:
•Pack 'n Play Playard or crib in each room or available upon request.

•In-room child care for ages 6 months to 12 years—in partnership with independent childcare provider Kids Nite Out. Some locations have fun-filled Child Activity Centers for ages 4 to 12.

•Kid-friendly recreation. All Disney Resort hotels feature kiddie pools (in addition to full-size pools) and many have playgrounds. Some even feature kids-only activities.
 
Disney Character Interactions
If your child is not frightened by the Disney Characters (if they are don't push them, they will probably grow out of it) there are many wonderful opportunities for your children to interact with them.  From autograph sessions to pictures with the characters, these typically make the most lasting memories for young children at Disney World.  The characters that are able to talk, i.e. Disney Princesses and Peter Pan are wonderful.  They really do a great job conversing with the children and making  them feel special.
 
The pictures and signed autograph pages in an autograph books are momentos that they will look back on for years to come.
 
Disney World Dining
When dining with young children you want to take into account how tired they will be and what their typical tolerance is for waiting.
 
I would recommend making Dining Reservations for any sit down meal ahead of time.  This will minimize waiting and guarantee that you can dine at the restaurant of your choice.  There is nothing worse to have one or more hungry children in tow when you find out the restaurant you wanted to eat at does not have any more openings for that evening.
 
Buffets also work well for getting your food quickly after being seated.  This will help for children (and adults) that are not in the mood to wait for your food to be prepared after a long day in the Disney Theme Parks.
 
As a bonus many of the Buffets are also Disney Character Meals, which adds another element to keep the children's attention during the meals.
 
Lastly, remember the high level of walking and exercise that you get during a typcial Disney World Day.  You may want to pick a Dinner Dining Time that is a little earlier than normal, so your children don't fall asleep while waiting for dinner.  That is why you want to take full advantage of the fact that you can make dinner reservations up to 180 days in advance.
 
Don't Forget Nap Time
One important planning tip is to not forget nap time.  Disney World Vacations can be exhausing for children and adults alike.  Keep that in mind and resist the urge to over schedule.  Nap time is important to avoid grouchy melt-downs at the least convenient times.  Note: The melt down you avoid may be your own!
 
Be Flexible
No matter how well you have done planning your Disney World Trip, remember to be flexible.  Some of the best moments at Disney World are the unexpected ones.  If your child wants to watch the street performer or the parade you wandered into, don't be afraid to stop and watch it.  Don't worry if you get off schedule or have to miss an attraction that was on the list.  If you are willing to go with the flow and be flexible as needed the stress levels will be lower and you will have an overall better vacation and more memorable moments to cherish.
 
Upfront Planning Reduces Stress During The Vacation
By spending the time upfront to plan your Disney World trip with your young children, you can reduce your stress and increase your vacation enjoyment.  Even people that typically don't like to plan will benefit from some basic planning for their Disney World Vacation.  You are committing too much money to your vacation to not spend time planning!