Granted a five year old probably should not be making decisions, but as some others have said, the OP really needs to understand why - after all Disney can be and is an overwhelming experience for adults, can you imagine being a child who for some reason has issues being forced to go. The crowds, the characters, fear of flying, etc.
I have a great nephew who was so TERRIFIED of characters (any characters - Chuck E Cheese, etc) that when he was promised a trip to WDW by his grandmother when he was potty trained - this was when he was three-ish - he reverted back to not using the toilet for over a year until my nephew and his wife realized - with the help of a therapist - that the whole issue revolved around not wanting to go to Disney because of the characters. I know this is extreme, but to him just the thought of it was terrifying. While many of us think being able to go to Disney is the best thing in the world, it just might not be for the OPs little guy!