Hi Lisbeth,
Your trip is only a few days away and you must be excited to travel with your sons. I love traveling with my daughters to this special place.
My first recommendation would be to think about past trips and what park they enjoyed the most and then go to that park. Each of my daughters have a favorite park and it is not the same.
The next park might be Magic Kingdom because it is the most magical in my opinion. Epcot is another good option because it never feels crowded. You have two separate parks to walk in with different experiences. Disney's Animal Kingdom is a great option because it is open and there is room to explore. This may make it easier if your sons like less confined areas. The last park I would recommend is Disney's Hollywood Studios as it is under construction.
You should make sure to take advantage of
My Disney Experience to book
FastPass+ as well as look at wait times. In addition,
services for guests with disabilities is a great resource and I would review it prior to arriving on Saturday!
Remember to grab Happy Birthday pins for the boys and let cast members know they are celebrating!
Happy birthday to your sons and have a magical day!
Beth