OK, so I just looked on ebay and found an HDMI to VGA lead, a 15" TFT monitor, keyboard and mouse all on buy it now for a grand total of £18. With the Pi that's £40 total and all I need is a case. Oh look, this external floppy case in my cupboard is big enough, a little hacking and I'm done...
..as for kids being messy, pah! My kids have never spilt anything on my PC stuff. I have and my cat is a menace, but the kids, never. If it's an issue, mount the Pi on the wall and get a waterproof keyboard, job done.