If one of the three monitors doesn't have a DisplayPort then make sure you get an ACTIVE miniDP -> DVI/HDMI/VGA adapter (DVI preferred if your monitor supports it) so you can do all three monitors from the single card. It doesn't look like the card you selected comes with one. Here's AMD's advice: http://support.amd.com/us/eyefinity/Pages/eyefinity-dongles.aspx
Also, if Dad wants to play games on three screens, get a bigger PSU (so he can Crossfire later) and get him at least a 6870 2gb card. If he wants to try three monitor gaming, the extra vram is very helpful. Be aware that if he likes it, he'll probably want to XFire later so make sure the build can handle that. Of course, if he isn't interested in the triple monitor gaming thing, your original setup will be fine for gaming on a single screen.