I disagree with your assessment. I myself am certainly not a lawyer, but the way I interpret that language is for something to be considered an act of terrorism it has to meet a criteria from section [1] AND section [2]. I agree that the planned drone demonstration meets 1c, but I don't think it meets any of the criteria from section 2.
If you're suggesting that because they're disrupting transportation activity then they are somehow creating serious risk to the health and safety of the public, then I wonder what you think of any kind of large scale protest march that closes down the majority of main roads in a capital city? Is that terrorism too?