I’m 32 and planning to attend a PhD program. I don’t have kids I am single and I’m fine living off a graduate student wage. I find research much more satisfying than what I’ve done in industry and am looking forward to the opportunity.
I discourage everyone from doing a PhD, but it sounds like you've made your mind up.
Be very careful with your choice of advisor and department, and if it isn't working, be ready to walk away--sounds like you have a career to go back to.