Nigel,
First off From a sunny but chilly St. Louis, Mo. It is nice to see some one like you taking an interest in kilts, But as a father let me just say don't push him to hard let him know that there are a lot of dads here on the forum who feel the same way as you do. I can say that as a dad if my son had come to me before I started wear a kilt and asked if he could get one and wear it I would not have thought twice about it and told him to go for it.
Be patient and all good things will come to you.
Good luck.