I think this is a fun idea, and I believe a first iteration of this could be done quite simply. I actually think you could get this off the ground for a few hundred dollars. Just doing some armchair estimating here, but I cannot believe that a metal QR code is going to cost more than $50. A GPS locator is $80 average, according to the Google. Weather balloons are remarkably cheap, $20-$40. With Helium, I would be surprised if it cost more than $250. After that it is all PR work which only costs your time. You can create accounts on the various social media sites and forgo any need for a website right now.

If I were you, I would start out by soliciting active Bitcoin related businesses to donate to the pool, as well as purchase supplies. If that doesn't pan out, try local businesses, or the ACM chapter at your nearest university. I would specifically contact under-represented organizations that could use some publicity also. Offer a firm deal, something like 'For $50, I will include your organization as a partner/sponsor in 2 press releases, plus at least 1 mention on each of our social media sites per day'.

Good luck!