Hi,
I am going to move you to our pre-trip board.
I think you need to take some time and try not to worry what the "experts" are trying to tell you. You need to find out what your family will enjoy.
May is a slower time at WDW, the weather is beautiful.
Try not to stress so much.
With young children, you may want to focus on the Magic Kingdom for them. Maybe on the day you go to Epcot, let the adults go, and someone stay with the kids and have a down day, go swimming, arcades etc. It's just a suggestion. There are things for young kids to do at Epcot, but not really, just "Crush" and the Clam mobiles.
Hopefully you will get more responses on our pre-trip board.
OhMari