Heck no! You’re never too old to write—for kids or anyone else. Lots of successful writers got their starts after their kids left the nest or after they retired and could focus on publication. There are plenty of marketing opportunities that don’t involve physical travelling, if that’s your concern. You’re already online—promote yourself through social networking and online writers forums, create a website and blog, write guest blogs for other sites, write articles for magazines/journals/newspapers that target your audience…. Savvy authors self-promote right from their writing nooks. This game is about passion and willingness, not age.