Uninteresting research area and contacting potential supervisors I've recently finished off my undergraduate degrees and am in the process of contacting various faculty members for MSc supervision. Recently I have been offered supervision at a research lab which I had previously worked with. However, I don't find the research that the lab is doing all that interesting. As a result, I've decided to contact a couple of different potential supervisors (both are world-renowned/highly cited) at a different institution. One of these potential supervisors has not replied to my last email and I'm thinking about contacting the other potential supervisor. My issue is two-fold:

1) If I move to another research area, will the lead supervisor at the lab that has given me an offer be jilted and could this adversely affect me in the future? Is it bad to reject an offer if I'm not interested in the research field? EDIT: The lead supervisor and another collaborator/co-supervisor are happy for me to leave if I don't like the research area. But I will still do some research at the lab over the summer holidays.  

2) The two potential supervisors are both in the same faculty at the same institution. The one that I have contacted already is the Head of the prospective research group whilst the other potential supervisor is a member of it. Both of them work quite closely together (looking at their recently published papers). 


Would it be unethical/bad for me to contact the other potential supervisor given that the Head of the group has not replied to my last email? It has been a week and a half since the last reply. Should I re-engage with the Head of the group? 
Should I tell the potential supervisor that I'm thinking of contacting that I have already contacted the Head of the group? Will the more junior member feel like he was the second choice and hence inclined to not respond?
Your undergrad supervisor would be a terrible person if they tried to attack you in the future because you didn't want to work with them for your masters. That's just crazy, but it does happen. You'd be better talking to the supervisor and getting their advice about what you actually want to do. They may know one of the other potential supervisors in the other area and be able to set up and introduction. 

Besides, even if your current supervisor did want to try to harm you later because you didn't want to work with them, wouldn't your rather risk that than get locked into research about a topic you don't like?

You should feel free to contact the more junior member of the potential research group. Do let them know that you've tried to reach the head, that you understand that they're very busy, and that you'd like to work with the group in the future.