Thanks everyone for your comments!
As I said, I use NoteBooks to manage relatively complex personal projects, like preparing an exhibition or moving house. But lately I have also started to use my iPad professionally, and I looked for a note-taking app to manage this. I thought about using NoteBooks too for this, but I felt that something a bit different was required, so I tried quite a few apps and finally (?) settled on Meeting Notes
It's not perfect, but it does the job for now. I can create a note for each meeting by importing a calendar appointment, and it comes with the participants already filled in, which is good. I can attach tasks to each meeting, or create tasks that are not meeting-related. There is an option to list all tasks, although I can't seem to find a way to display open tasks only, I need to write to the developer about this because it could become a major flaw as time goes by. Otherwise it works pretty well. The interface is not very good-looking and the icon is positively ugly, but it's easy to understand and use and it has the basic functionalities I need. So I have adopted it for the moment as my work tool.