Legal? - SPOT Helium Balloon Race

Hi,

This was a crazy idea I had that my son thought would be a lot of fun. The
question is whether or not it is legal or advisable.

The idea is to tie a bunch of helium party balloons to a SPOT unit, then let
it go and see how far it gets. We would chase it down in a car.
Theoretically, we should be able to follow it and know exactly where it
lands from the SPOT tracking data - send to a PDA or monitored using a PC.

I thought it would be fun to get my 11 year old son and perhaps his science
class at school to help design it. They would learn a lot in the process -
such as calculating the number of balloons required, analyzing the weather,
etc. I was planning on including a parachute so it won't land hard if all
the balloons pop, and a dish shaped base to help it land right-side up so
the SPOT tracking data can be broadcast to the satellites after landing.
We'd also attach a note with our phone numbers. We'd try to keep it as
light and simple as possible so that it would not do any damage to aircraft
that might happed to hit it. I think the odds of it getting hit by an
airliner are extremely slight, but I certainly wouldn't want to cause any
issues with airliners and their passengers.

I think it would be a fun adventure that may even help convince my 11 year
old (nearly 12) son that doing glider retrieves would also be fun when he
gets his driver's license in less than 5 years.

But I don't want to do it if it is not safe, or not legal, etc. I don't
want to "take my chances" that it will be safe - unless the risks are
miniscule.

I look forward to your feedback. I imagine that it won't be positive, but I
just had to ask... It sounds like a fun adventure.

Good Soaring,

Paul Remde