I think it could work, but definitely finding the firm is going to be critical. Certainly here, there's huge differences from firm to firm in the way they approach flexibility for their staff.
Also picking the right area of law, which may come with a bit of experience. Like I said, the adrenaline-junky lifestyle of civil lit just wouldn't work for me, but a more process-driven area like property might suit me better in the future. And figuring that out is probably going to be part experience, part trial-and-error. But I'm certain it can be done, it'll just require a lot of hard work and probably some flexibility in your idea of the 'dream job'. Actually the 'dream firm' is usually more important, and like I said, if you need flexibility, that probably won't come from one of the big flashy ones, especially when you're starting out and finding your feet.
Once you rack up experience in a particular area, the game changes a bit, because firms (here at least) tend to he more prepared to be flexible if you're bringing experience to the table...to a degree!
Working in small firms v's large firms is a completely different experience and environment. So keep an open mind about smaller, less flashy firms.