The actos de acompanhamento are later defined as "actos de moderação", i.e. the exercise of the functions of the chairman and secretary of the meeting, while "actos preparatórios" are defined as "actos convocatórios" (the call for a meeting) and "actos posteriores" as "redação das Actas" (drawing up of the minutes).

So, to put it simple and clear, I'd avoid something like "acts supervising/monitoring/accompanying the meeting", but instead go for "acts preparing the meeting, acts during the meeting and acts after the meeting" or "acts preparing, during and after the meetings".

Acompanhamento in this context is not a follow-up (as in acompanhamento médico) because a follow-up generally refers to something accessory that is done after an action/event.