Ditto Melissa's recommendation with the Well Trained Mind. Since you've been HSing for so long, you probably know all about it, but still, I just have to share! We started HSing my DYS in January, and this book literally sits next to my Bible on my nightstand. Following this model is so popular that most of the gifted children in our HS charter also follow it.
Like Melissa said, you have to adapt it (and any program) for the specific needs and interests of your children, but it's easy to do. I follow the general philosophy, and then handpick my own materials. We do use Story of the World (which will lead you down all sorts of paths with the extra reading!!), but I find WTM's language/math recommendations too basic. For more substantive materials, I love Rightstart Math and materials through Critical Thinking Resources (Mindbenders, Word Roots, Reading Detective, LanguageSmarts, etc.)
With science, we love R.E.A.L. science, which you can easily do at home. It is designed for 1-4th graders, so it would be perfect for both of your children. Story of the World is also labeled grade 1-4 and truly does work for any child in that range. (We're also starting Apologia Science, but that's only because our co-op is going to do labs through it.)
Btw, we tend to like the immersion approach much more than the spiraling, which is too redundant for many PG learners. I find that this opens up a lot more opportunities for what we want to study.
If you'd like to swap ideas, you can always feel free to PM me, too.
