Hello and thank you for your post. There are some pubs near the Valley you could try like The Royal Oak pub in Charlton Lane and The White Swan Pub in Charlton Village but am not sure how family friendly they are as I don't visit the pubs on match days preferring to use the stadium. Avoid The Antigallican near Charlton Station as this pub is for away fans.
You could also try Cattleya in Charlton Church Lane, nearly opposite Floyd road which is a small Spanish/Thai restaurant usually very popular with Charlton fans and welcoming of families. Also there is Bartram's Bar by the West Stand of the Valley which is family friendly.
I don't think you'll hear the songs before the match to be honest as you're more likely to hear 'Valley Floyd Road' on the way to the game or inside the stadium.
I hope you enjoy the game against Walsall and bring over some good luck as the team could do with a win after a string of poor results.