I have wanted to make a pillowcase dress for my girls since they were babies. They are now almost four and six. Obviously, I'm a better dreamer than doer.
Recently I found some really cute pillowcases for a quarter each at a thrift shop, and that was motivation enough, finally. I used the handy tutorial at Rostitchery to do the dress. However, making a pillowcase dress for a tall almost-6 yr old presents certain issues.1) You should restitch the side seam to reinforce it at the bottom, especially if it is a vintage pillowcase. When the child is older like mine, there is not as much room to swing their legs in the pillowcase. This can cause a lot of strain on that seam.
2) I was initially happy that one of the cases was a king size, because my oldest girl is tall and I love the look of a long dress. However, after learning point 1), I will be hemming it up to a knee length because the longer the dress, the less room for leg swing. Alternately, you could fashion slits in the sides using more bias tape. Or, you could always make a pillowcase tunic or shirt instead of a dress.
3) when using this tutorial for a kid older than a toddler, you will possibly need to add depth to the armscye and possibly more width to the elastic. (I used a 4" armscye and increased the elastic to 6.5 inches). Also you will need a bit more bias tape than she has listed.
4) and lastly, kids that are older will look a little bare in a vintage pillowcase if it is thin and white like the ones I have. You can clearly see her underwear through the cloth. So, I will be adding a built in lining to cut down on the peekaboo factor.
So much for this easy and quick dress. But, it is still adorable, and comfy.