I think the best way to do that would be to sit down with them first to find out what they think is or isn't working and to discuss ways to improve the office. If you can get them involved in the change process you'll get a lot more buy-in. They may even come up with similar or better ideas.

But be sure they understand that while you're allowing it to be a collaborative process, it's you who has to make the decisions and not all decisions will be popular, but they are what's best for everyone in the long run.