How to send end-of-the-year wishes in academic environment?

Currently I am working in a research group where there is much emphasis on the interpersonal relations.

I want to write an email and send it to my direct supervisor, with whom I have closer relations compared to the others. But, I also want to send my wishes to the whole group included the head of the group, but I want to do it in a fashion which will sound mildly formal but with a sense of respect and hierarchy in it, and not friendly and too informal.

Any suggestions, or nice emails that you have received?