English Medical Social Science, Sociology, Ethics, etc. With or without apostrophes? Title of a paper

Patients, relatives and medical professionals' experiences with therapy groups
or
Patients', families' and medical professionals' experiences with therapy groups
?

This is the title of an academic paper I am editing. (Well, not exactly, but the grammatical question is the same.) It is generally well written by a non-native speaker of English.
I would rephrase it, but as it is the accepted title, that is not possible.

I received it without the apostrophes, and added them, but somehow they look wrong.

The paper is for publication in the US, and of course, I checked in the Chicago Manual of Style.
As far as I can see, the rule is:
Gilbert and Sullivan's operas (only one apostrophe, as the possessive applies jointly to all their operas)
BUT
Gilbert's or Sullivan's mustache (apostrophes for both, as each has his own mustache...)

The paper goes on to discuss how the therapy groups were experienced by the different participants - how the patients felt they benefited, whether the groups were helpful to the relatives, and what they thought, and finally the professionals' assessments and comments.

In short, three sets of experiences, although they overlap, and are all discussed together in the paper.

I am inclined towards three apostrophes, but I know I will have to explain this to my client.

All comments gratefully considered!