I would suggest testing if you can swing it, especially due in part to the fact you said your family may be heading the military direction. Moving around is not optimal when you have a gifted child as some of the places they stick you (we are Army), educational opportunities are minimal at best and you need all the backing you can find to get through to administrators who tend to care less because they know you are short termers in their area.
As for having one of your children go to public school and keeping another in a homeschooling format, we will be doing exactly that next year. Our 5 year old twins will be heading to 1st grade in the fall and they have no problems in the public school system. It could be faster but they are a good fit no matter where they go. Our oldest (DS8 going into 5th grade) is an out of the box, bad fit with public schools and will be homeschooled through a virtual school and other side subjects of our chosing. He is all for the idea however because hes tired of the bad fit at school so we don't have the issue you seem to have with your daughter wanting to be at school if your other daughter goes.
Good luck, but maybe look into testing at a local University with a grad student possibly? That will at least give you an idea of what you are looking at but not with the huge price tag that comes with some of the more specialized psychologists who test gifted children.
