"I purchased 2 of these for our trip to disney this summer for my 4yo & 7yo. The pants are perfect for my older son (will have to take in the elastic for my younger son). The shirt is a little short on my older son, except the sleeves. They fit him perfectly. The shirt is too big for my 4yo. They are well made for costumes and the kids will be able to play in them after our trip or I will probably resell.
These would probably be best for your 5 1/2 - 6yo in terms of fit."