Hi Mary - My advise to you, is one step at a time. It is true, some engineers in some jobs work very long hours. However, some do not, that is choice you can make for yourself when you are looking for a job. I know women who work 32 hours a week and never more so that they can have time at home with their children. I myself often take two hour lunches to get things done and make up time when I can.
So my advise to you is that if are interested in civil engineering do it. Find a job you like and work hard. Then take one step at a time, find a partner to have kids with, take about the fact that maybe your partner want to stay home full time, or talk to your company about an abbreviated schedule, or find a job with flexible hours, or stay home full time. You get to make these choices, but don't skip out on a career you like, because of things that might happen in the future.