We're a very musical family and we've seen some of this reluctance to practice too. Thankfully, it seems to really help talking to your kids about it and emphasing effort over talent. My 13-year-old daughter is now learning three instruments and as she gets better, she's started practicing more and more. I'm a flute player, but started learning the bass just last week. The kids see me practice every day and that helps too! We need to model what we want to see and show them what persistence looks like.