I agree with ColinsMum that doing something more unschool-y might be the way to go. It doesn't have to be full-on unschooling. That would strike fear in my heart, personally, though I believe strongly that there are ways to make unschooling work wonderfully well for kids. How you approach homeschooling is really more of a personality issue than anything--both your child's and yours!--and I am not that personality. But there's a HUGE middle ground between no set curriculum whatsoever and doing exactly what some teacher's guide tells you to do.
My compromise is to be very child-led, offer many choices about what DS8 can do, but still have some fairly flexible requirements. We have "math time," when he must select one of the many options I provide that are acceptable to me as math. I choose the options based on his specific needs. Some we use a lot, some we never touch. Some are game-based, some are very traditional worksheet-type things. As long as we eventually cover all the skills he needs, whatever he picks from the pile of options is fine.
He has to do each subject when it's time to do it, unless he gets on a roll with something. If that happens, I make the call about whether it's more productive to change gears or to amend the schedule to let him keep going. Usually it's worth it to let him keep going and just catch up on the other subject(s) later. If he's excited about learning, then it usually doesn't make sense to stop him.
The central idea here is that he and I are partners in his education. When we first started homeschooling, I told him that I am making a promise to the state that I will be sure he gets a good education, and that if I can't provide that, he has to go back to school. So there are things he must learn. But how he learns them and when he learns them are flexible. On bad days (of which there are surprisingly few...), I remind him that if he is unhappy with what he's learning, then he has to work with me to help me find something else for him. It's his responsibility, too. That works for us. It might not work for all kids, not even all HG+ kids, but it works like a charm for him. Feel free to use or ignore...
BTW, we started HSing when he was 6, so these sorts of conversations are not impossible with a 5yo, depending upon the child. But giving your DD some responsibility, stressing to her your own responsibility, and being very flexible about what she studies could be just what you need. I can tell you for sure that giving DS8 a great deal of control within certain boundaries virtually eliminates fights around here. Plus it is encouraging him to view his education as his own responsibility. I don't know that I ever really felt that way--even in grad school!--so I think that's a good side-effect.
Hopefully there's something mildly useful there for you...
