Mark - this looks fantastic and, on the one hand, I do applaud you for creating something for Dads and Daughters specifically. On the other hand, don't call this a book for parents and children as that's clearly not your intent.
I do strongly believe we need to provide more encouragement for girls and young women to get into the STEM/STEAM careers and interests. And it is somewhat encouraging to see things like your book and the Goldiblox system out there to do it.
But both of those things also fly in the face of the goals set forth for other supporters of women in STEM. The argument thus far has been that these things are marketed to boys and men. Does it then make sense to counter it by only marketing it to girls and women? Or does it make more sense to completely shift the marketing so it's not just for one gender, but for anyone who expresses an interest?
The reality is, I would buy this book in a second to use with my five year old son. There's lots of great stuff in here that I know we'd both have fun doing. At home, we have not reinforced the idea that "this is for girls" and "this is for boys", but he definitely has a sense of when something is sold to a specific gender. Yes, this is probably the fault of TV and gender stereotypes leaking in through other channels (and I'm sure the fact that he doesn't own anything pink or purple puts some of the blame on his parents as well) but the fact is he recognizes when something is being marketed to girls and clearly feels it is not intended for him.
Mark, this is less a criticism of you than of the whole "more STEM for girls" movement as a whole. Given that girls tend to prefer things that are more on the pastel end of the color spectrum (For all their "fight the pink aisle" rhetoric, Goldiblox are still pretty stereotypically "girly") and boys trend toward the darker colors, I don't think we'll ever really get to a place where these things are gender neutral. So it's fine, really, to have a book for Daughters and Dads. But, please, don;t market it as something for all parents and all kids. Just as girls get frustrated looking in science books and seeing only boys, boys feel the same when something is clearly marketed to girls.
A better solution - show experiments conducted by father and son AND father and daughter. For that matter, show experiments with mother and son AND mother and daughter. And, for Pete's sake, don't relegate the mom stuff to kitchen chemistry - for Mother's Day this year, give Mom a soldering iron!
If you really want to end the gender bias in the sciences, make it all inclusive.