Thanks for the responses, everyone.
OK, so I think I'm hearing that electrical noise due to proximity is not a top concern, but that the mess is.
I already do all my wood working outside in the driveway near the shed, and was planning to do anything like grinding outside as well. The only issue I see is that TIG (and MIG, for that matter) do not seem like outdoor-friendly processes, unless the day is totally windless. I guess a welding table with some kind of fences could make that work. Most welding tables are steel and quite heavy. I'll have to make a compromise if I want to be able to bring it in and out. Then again, in ham radio, everything is a compromise, all the time. :-)