I've kinda had similar experiences with songs.  I notice that if my thoughts shift to wondering or feeling something, it can bring a song into my head whose lyrics are about what I'm feeling.  That's not exactly like what you are describing though is it?  It sounds like you're attributing a song you thought of all morning as leading and preparing you for an important moment with your son. 

This is a little bit off the subject, but speaking of songs, I remember when my ex and I were dating, and one day spending the day together I had "Glow Worm" in my head all day and I kept singing it. Since it's an older song and you don't hear it around usually, it was indeed odd that it was stuck in my head.  It was driving him crazy and he finally told me to knock it off.  I told him I was sorry, but I couldn't help singing it since it was literally playing in my head.  Well it came lunch time and we were trying to find a place to eat.  We found a Brick Oven Beanery, never been there before, and walked in.  Guess what was playing inside?  Yep.  He just looked at me and said, "Did you set this up?  You planned this didn't you?"  Consequently, the restaurant was closed unbeknownst to us, and we were met by an employee who was surprised that we even came in.  I guess we were so focused on lunch that we didn't even see all the signs.  I chalked it up to fate bringing us there, I don't know why though.  Maybe just so I could finally get relief from the song.  After that, it wasn't stuck in my head anymore.   

Bardo,  Most def.!  songs can be a form of guidance or confirmation. Its happened to me several times. The first time it happened it was guidance from a song on the radio that kept playing no matter what time I got into my car heading to the hospital to visit my grandmother. Finally, I listen to the words and it was a counrty song "Holes in the floor of heaven" . Its about a boy whos grandmother dies on his birthday. Yep, you guessed it, a month later, my grandmother died on my birthday.
I also hear songs ehterically. Not in my head but like I tap into the radio waves.
COol stuff!