It depends what you want to use the laptop for. If you want it so that the entire family can use it, you'll want a laptop that has a larger hard drive and faster processor, which means a higher price tag. Or, you could go the cheap route and grab a few netbooks. Netbooks are really good at word processing, basic multimedia applications, and Internet access. You can get a netbook for about $200, whereas a laptop as mentioned above will probably cost $600. And if you get a single laptop, the hard drive will fill up and people will fight over who should delete what, and no one is going to be happy with that. Plus, all those user profiles will seriously cut down on your computer's speed. Save yourself and get netbooks for everyone.
Unless, of course, you can afford laptops for everyone, or at least two for your family. That would be preferable to netbooks.