No need to get agro. This is the problem with so much stuff online is it's designed to get people worked up - the worst case is presented to get the headlines, or alternatively it's the government line - it's all ok. So I'm with laughing gas on this.
It's really hard to find good info. When you find a report it says, "radiation levels measured as high as" rather than saying the average. Or they use Becquerel rather than sieverts, the adjusted measurement for harm to the body, which can vary vastly in meaning depending on how they take the measurement and what it is measuring.
From what I've found the exclusion zone is based on an increased cancer risk from exposure for a year raising lifetime cancer likelyhood from 42 to 42.2%. For five days this would raise it .003%. And these percentages are thought to be over reality because it's very hard to measure increased risk like that. Let's say it's worse than the government says(probable) and motegi has levels the same as the exclusion zone (at a square of the distance 60km? it would have to be 9 times worse - admitedly these things aren't as simple as that) . Then that's something like the risk. They should be careful of where they get their food and water from, injesting stuff is far worse.
Here's an interesting comparison sheet of radiation levels. http://xkcd.com/radiation/ Though I'd take the fulushima measurements with a grain of salt. It's a good approximation of the relative sizes of doses.
What's going on over there is horrific, granted, the industry is dodgy as all hell, particularly in Japan, one of the worst place on earth for it, and I don't like nuclear power at all but at the distances we're talking and, particularly, the exposure levels they'll get in three days it wouldn't stop me going.
But perhaps with everyone getting so scared they should, for piece of mind, just cancel it anyway.