My daughter sings better than anyone in the family. I wasn't always confident that she would be musical. She was always expressive, but not always in tune or with the beat. She's always had a lot of style.
It doesn't matter when children start singing in tune. Sometimes it's as early as 3 or 4, but often not until 5 or 6. My daughter was still not consistently singing intune until almost 7 years old.
It does matter that we sang and had fun all these years. The best fun we have is when we improvise together. We made up the "Poopy Blues" a couple years ago. She never forgot it. The second verse is the "Ploopy Bues" or the "Bloopy Poos." It's all the same imagery and we giggle about it.
Sing and have fun. That's the best a family can do.
Around the Seder table makes it just a little more special.