What you say to your child is important. But what may be even more important is what you don't say. Parents often convey their attitudes and expectations in indirect ways. Not every child, of course, is destined to seek a career in science. But every child should be able to become a scientifically literate adult, and all children should know that if they choose science as a career, they can succeed.
Parental expectations can encourage positive attitudes and personal best.
Don't forget, too, that girls are every bit as curious as boys are about science. Buy your daughter that tool kit. Recognize the difference between clutter that comes from enthusiastic activity and the sloppy piles that result from neglect. Don't forget about safety. Supervise young children as needed.