Jamie,
I think you're an amazing parent to be willing to take the leap to HSing proactively! It's a big, scary change--at least it was for me and for most of the people I know who are now HSing--so to be thinking ahead--regardless of what you decide to do--is just really wonderful. Please pat yourself on the back for me, would you!
I think it is very possible to "see the writing on the wall" and know that something has to change eventually, even if things are fine at school for now. I don't think you have to wait for a serious problem to decide that you can do better in a different school situation. (Not everyone agrees with me on that, BTW. So I may be in the minority with this answer...)
With girls especially, I think "stealth GT" problems are much harder to ID and can really hamper a GT child's development. "Happy" may really mean "working hard to fit in," and that can lead to problems like underachieving, perfectionism, and depression. I'm not saying these are happening in your children's cases, but I think it is a danger to watch for.
So I guess I think my answer to your question depends upon what you mean when you say "Currently both girls are pretty happy in school and not having major problems." What constitutes "pretty happy"? What not-major problems are they having, and what would constitute a major problem?
If the girls truly love their public school and would be miserable without it, then I'd advise you to leave them where they are.
If "pretty happy" really means "not very happy," they like the idea of homeschooling, and there's an active HSing group in your area, then it might be wise to investigate a bit. You have the time to do some research, and you may find that it is a much better fit for your family than public school. I'd also recommend looking into daytime child care, since if you are even a little bit like me, you will want some time without the kids to think, work, read, run errands, etc. Having that in place early is important!
I don't think you have to accept "good enough" for your children's education if you can do better than that. But I think you want to be sure that your kids are in favor of the change and that you have the local resources available to make the change a sensible one for you.
If you have specific questions about HSing itself--what it is, how do get started, etc.--I'd be happy to talk with you about it more in depth. I got lots of help before I made the decision to switch to HSing, so I know how it is and I'm happy to answer any questions you have.
K-
