Thank-you Bob and Cryptofishist.
Bob, you have given me some food for thought. I appreciate your honest response (my initial reaction to it was a bit thin-skinned). I do get why plant materials on the playa are a cause for concern, even more than other MOOPish things, but you've convinced me that they're more problematic than I had imagined. I'm not sure that I'm [i]entirely[i] ready to abandon the idea just yet -- but between you, Eric, trilobyte, and Duncan, I've certainly got a lot of reasons to be extra-cautious and not do it unless I'm sure I can do it right, which I'm not yet. I really appreciate all of you for sharing your ideas and concerns.
Cryptofishist: I love seed paper! I had also thought of envelopes as a container, but I had decided against the them because they can blow away and then will break down when they encounter moisture, allowing the seeds to germinate where they land (I had also thought of zippered plastic bags, but I decided they're still to blow-away-able and too MOOPish).
I think a proper container would be a little tin, something reusable and buyable in bulk (like this: http://www.containerandpackaging.com/item/M515
), with seed bombs inside, sealed with tape and labeled with instructions (including what region would be appropriate for planting those seeds). BUT.... even with the precaution of a solid container, there's risk. Someone could empty the tin to use for something else, and then lose/loose the seed bombs on the playa. Like I said, if I decide to do it, there are plenty of reasons for caution, and it's possible that I won't be able to get the risk down enough to make the project worth doing.
I probably already know the right answer. I'm just not quite ready to say goodbye to the idea yet.
If you want drama to stop following you everywhere, try letting go of the leash.