I think, maybe “descriptive or hermeneutical phenomenology” fits best with your intended study as you are interested to understand the experiences of five participants. This type of phenomenology refers to the study of personal experience and requires a description or interpretation of the meanings of phenomena experienced by participants in an investigation. If you want more details about the typologies of phenomenological studies, please read the following document attached here with.
Descriptive phenomenology would be the best option. it would afford you great time engagement with participants for you to understand their experiences. Also, analyze the findings using the Interpretative Phenomenological Analysis (IPA) where you present the findings using the rich experiences from the students. It will make you lavishly present the thick descriptions of participants while heavily quaoting their experiences. It would be a wonderful study. All the best.
If possible it is best to not start a Phenomenological study with a limited number of participants. The process of collecting data in a Phenomenological study is to analyze the data as you go along and use that analysis to point to other aspects of the phenomena being studied. In a study I did on experiences of previously unconscious patients, one patient described being more alert when he was moved. I went looking for other patients who were moved during their unconscious episode. In fact, patient do report being more alert when moved. Unlike Quantitative studies it is difficult to tell how many people will need to be interviewed and/or observed. If you can avoid restricting the numbers at the beginning, you will have richer results with whichever Phenomenological method you use.
Good luck to you. Phenomenology is great fun, too.
I don't think that whether we are talking about 5 or 12 participants should be the deciding factor. A more important question would be your topic and the level of interaction between the participants you hope to achieve within the study. I can think of situations in which a focus group might be the best way to go.