Hello, I have been in this situation.
Here are some pointers:
Firstly, it’s more to do with your feeling than theirs. Did you not used to dislike your boss and crib about him with these friends. Now you are that boss, remember this. The relationship will not be the same again.
Have a chat with them and tell them that there will be a change and fortunately, or unfortunately, they will have to adhere to it.
In my case, they were couple of cases who just did not accept my being a boss. To be honest, I was happy when they left. Changing mix of the team also helps. If required hire more new people.