Being put above your friends changes the arrangement whether anybody admits it or not. A few will push to see whether the old footing still applies, and trying to stay the mate while holding the job tends to lose both. What holds is being predictable: the same rules for everybody, including the people you like.

Decide your two or three lines before the shift and apply them to your closest friend first. Say the awkward thing early and briefly rather than letting it build. Being fair annoys people for a week; being arbitrary annoys them all summer.