Wow...it's been a long time since you've had breakfast at McD's, huh? They've stopped serving breakfast at 10:30 for YEARS now!
I understand the fascination with the Egg McMuffin -- my family loves them -- which is why I make them at home now. Perhaps you can make Jullian one at home as a surprise. Five year olds are easily amused by things like that.
As far as a Happy Meal, I really don't think it is McDonald's responsibility to give Jullian one. I think YOU should get him one for the language you used in front of him!
I'm not judging your parental skills, but just know that if a young child wants a certain thing to eat that they can't get, you have a potential "temper fit" arising. Don't make a situation worse by throwing out explatives and attitude yourself ! Kids pick up on your anger and next thing you know, you have an inconsolable child on your hands.
Good Luck to you and Jullian. I hope your next McD's visit is a pleasant one!