I've mentioned before that we sing/teach the older hymns to the kids. We've taken a little bit of a break from that over the last few months since the music they learned for our Christmas concert, but we've recently gone back to nightly hymn singing.
One of the things I like to do from time to time is go back to a hymn they learned a a year or more ago, and see if they remember all the words. Some of them they do, like Onward Christian Soldier (they love that one, they get to stand up and march!), but many of them they tend to forget the lyrics, and only sometimes remember the chorus.
One current example of that is Victory in Jesus. It's been a few years since they first learned it, and when they did learn it, it was all by repetition, since none of them could read yet. Now that they can all read (except for Ruth) I print out a copy of the lyrics for each of them so they can sing along with words in hand. It makes a big difference in how fast they learn new songs, and refresh their memories of the older ones.
I'm a firm believer in the idea that all kids should know the old hymns. Maybe that makes me old fashioned, or maybe that makes me culturally irrelelvent - I really couldn't care less. I know there is nothing sweeter than hearing little kids sing songs such as Guide Me O Thou Great Jehovah or Be Thou My Vision. Old songs rich in doctrine that exalt the Lord's grace and mercy, sung by wee little voices.
I hope some day they appreciate that their mother made them learn the old hymns. I hope someday they teach them to their children, and let it be a family tradition for generations to come.