Wow, I see a lot of good points, well presented, on both sides. This is tough! I'm sure you will hear stories from others that either decision could lead to great success.
My own philosophy is to follow the child's direction, so I agree with you. However, your husband has a very good point as well: maybe your daughter will like math more if she is exposed to more engaging content.
My DD11's experience is not exactly like this, but we have chosen to let her take the lead and tell us what she needed. I knew she was really good at math when she was in K and 1st grade, but didn't do anything because she didn't really care about math. She has been obsessed with music and theatre since K, so she is always busy anyways. Since maybe the end of 3rd grade she expressed an interest in math. So we bought Singapore Math books for her to do at home. We didn't set a routine for her. Sometimes she would do Singapore Math everyday for a week; then the next week she wouldn't touch it at all. We just let her do whatever with it. Then at the end of 4th grade, she asked me about acceleration at school. I talked with the school and the district and settled on a plan for math. So in 5th grade she was accelerated at school and finished 6th and 7th grade math, pre-algebra and algebra. In the fall when she starts 6th grade she will take accelerated geometry.
My DD is the type of kids who have very specific ideas about what she wants to do. So we are comfortable letting her take the lead. Sometimes she doesn't want to explore acceleration even though we wish she would (such as world languages). But if she is comfortable with a group of kids or a teacher or simply doesn't feel the need to rush forward, I think it's OK. Kids are kids and having a relaxed childhood is a luxury these days but really has its merit.
