Bring the costume! The little ones are so cute in the costumes (and you're more likely to get little bits of magic from around the parks when they're in a DIsney costume. We usually have princesses or fairies, but have also traveled with Minnie, Tigger and Pirates. And will be again this trip. For the little ones, it doesn't matter if it's halloween or any other time of year - they can dress up all the time.
For our First MVMCP our (then) baby was dressed as
Aurora when we went to visit the princesses - Prince Phillip was there and kissed her - and she woke up! It was so wonderful to see her sleepily smile and reach over to hug him
If he wants to wear the costume from sun-up to sun-down, let him : ) no one will think there's anything odd about it.
We just got everything for our trip in the mail! Very excited.