[I'm going to copy/paste my reply from a nearly identical thread]
I realize I'm a bit late to the show here, but for the benefit of anyone else who may happen on this thread:
I had thought of the possibility of Electromagnetic Radiation in the front, near the motor (particularly when the magnetic strip on two of my gift cards ceased to function), but I wouldn't have thought of it occurring near the batteries. I certainly wouldn't have expected it to reach so high as 100mG. I've done some research a while back on the association of EMFs and various health issues, and I'd say your concerns are valid. As others have mentioned, singular exposure for a limited time doesn't seem to have any noticeable effects. However, repeated or long-term exposure has been potentially linked to health effects in all humans, with children being particularly susceptible to any sort of energy radiation. Still, if your kids wont be spending much time in the car, I wouldn't worry too much. If you really want to do something about it, I believe copper or steel sheeting (or perhaps a combination of the two) would effectively block/absorb the EMR. You'd just have to do some experimenting with it.
EDIT: So, I recently took my FFE apart to see how the battery is put together and such, and discovered an interesting caveat: the primary cables between the batteries and the motor are shielded, much like a coax cable. The battery itself is entirely encased in a steel box. So, I suspect that perhaps the EMF is coming largely - if not entirely - from one or more small locations, such as where the cables terminate to the connector on the battery case. Thus, if a person wanted to, it may be fairly easy to shield particular locations and completely block any radiation.
2013 "Candy" Blue FFE