I have collaborated on a certain topic with researchers A, B and C, where A is my PhD supervisor (I'm now a post-doc), and B and C are senior colleagues from different universities. The collaboration lead to a number of papers, in which I was the main author, while A, B and C made important contributions.
I'm now working on an idea that continues the research direction of this earlier work. Since I already got pretty far with the execution of my idea, I don't expect much additional benefit from involving A-C at this stage. In fact, I would prefer to publish this work without them, since I'm in a career stage where the common advice is to assert myself as an independent researcher.
However, I have the feeling that A-C might be disappointed if I don't involve them - I certainly would, if I was in their position. Is there an etiquette for tactfully dealing with this kind of situation?