Here are the sleeves I am talking about
If the sleeve elastic is independent of the seam it's super easy to fix. All you need is a seam ripper. These are sold mostly everywhere I have even seen them at Kroger. Here is mine
What I did was pull the elastic away from the material where I could see those stitches holding it together.
I used my seam ripper to cut those stitches all the way around on the top and bottom of the elastic.
When I was done I had the elastic attached to the middle seam and nothing else. Be sure when you go to cut the only thing on the seam ripper is the threads these things are sharp and will cut the fabric so just take you time and watch what you are doing so you don't get any holes in the shirt.
I took a pair of sissors and cut the elastic out. Now the end of the sleeve is open and not tight on my daughters arm!!
After a wash the little holes will disappear and you will be the only one who knows!!
If the elastic is in a pocket on the bottom of the sleeve or is part of the hem at the end you will need to go back and re hem the sleeves so they don't start to fray.
Hope this helped someone.