I don't know your sewing ability but have you considered matching x-kilts? They are fairly simple to make and your son can help. He could help you go to the local store to pick out the BLUE material for the kilt. He could help hold the tape measure when you are marking the kilt etc. I know that a 3 year old normally provides negative help, however, it is the bonding, father/son thing not the amount of help. Considering the total cost of a childs x-kilt you wouldn't cry as he walks out the door the first time and heads directly to a mud puddle.