Hi Yessenia!
Without any consideration of the crowds, which requires knowing your exact date of arrival, I recommend visiting the parks in the following order:
- Epcot
- Disney's Hollywood Studios
- Disney's Animal Kingdom
- Magic Kingdom
You could switch around the Studios and Animal Kingdom. I recommend visiting Epcot first because while some aspects of it are very child friendly, others are less so. Your children will be excited to be at Walt Disney World and probably won't be phased by the less child friendly aspects (for example, my youngest son does not like spending too much time in the various countries in World Showcase). In other words they won't say "can we leave Epcot and go back to the Magic Kingdom", because they won't have intimate knowledge of the Magic Kingdom yet. Likewise, I recommend saving the Magic Kingdom for last. As the crown jewel of the Walt Disney World Resort, a lot of children would rather spend all of their time in there. Of course, this order may be impossible because perhaps you or other members of your family may want to visit the Magic Kingdom first!
To base your decision on the expected crowd level, I recommend visiting the independent website TouringPlans.com. They have a crowd calendar and offer recommendations on which parks to visit on which day. They also provide plans to maximize the number of attractions you can enjoy while minimizing your waits in lines. I'm a huge fan of their work and highly recommend getting a subscription to their site to access all of their information. Their recommendations are based on a lot of mathematical analysis and years of data collection!
Have a magical vacation and write back if you have any more questions!