I want to order shirts for my boys. I have an 8, 7, 4 and 3 yr old.

Do the shirts run small. The 2 younger usually wear 4's, but I'm thinking the xs(2-4) would be too small. I was going to order them a small, order my 7yr old a medium, and my 8yr old a large?

All of my kids are average size, so I'm a little nervous I may be ordering too big!?!?

Any advice? Thank you!