OK now I’m getting confused (I knew I would) because I’m getting conflicting opinions. Some say, please do explain, other say, I don’t want to know the details.

Well me personally for a kids birthday party I don't think it requires an explanation if you don't intend on coming ... now a wedding or engagment or a "special year birthday" like an 18th or 21st THEN I would offer an explanation but seriously for a 5 yo if you can't make it you can't makeit ......

I think society thinks it needs to explain its actions for fear of reprimand(sp) or something but really a "sorry we can't be there" is all thats needed