I do not think managing people who like to challenge is ever easy, it is not you that has the problem it is the people who through poor personal communication skills resort to being as you describe.
When taking over a new team I always tried to listen to them first to find out what their views were, workout who were the ones most likely to be verbal and often initially quite challenging. Experience taught me that if you can find out why they are unhappy and behave in a certain way, you might be in a position to change things and if you show you are trying to understand their point of view I found staff were suddenly much more receptive.
Good luck, you will be fine just take a deep breath, stay calm and face them, much better to face it than dread it!
