Being super cautious around lighter than air craft would be my advice. It's not really beyond logic that a UAS could easily slit a balloon envelope in a heartbeat. Given the still somewhat flaky control and navigation systems used in the DJI birds today, aside from outright disaster, it wouldn't take much for a balloon pilot to lodge a complaint with the FAA which could lead to an investigation, which can be a pain in itself.
Years ago, I was photographing an entire balloon ascension from a manned aircraft (door removed). Was well clear, of all the balloons, circling them as they rose. Sure enough, I got a call from first the chief of the local class d tower stating a balloon pilot claimed I was too close, followed by an FAA investigator. Had to do a telephone interview, and a follow up call "cautioning" me regarding flying around balloons. I was in the clear, as I had been advising the tower during the flight of both my position and intentions (which the balloonists may not have been aware of if they were not monitoring the tower frequency).
I've thought about getting such images/video with the
M2P, but have declined because it's just not worth the potential outcomes.