Stop in for a cup of coffee

Well, I got news today about a prior job that I applied for. Not the one with staffing problems, this one I interviewed for back in Dec. I made it to a 2nd interview. They told me there will be a writing exercise with follow up questions about supervisory and leadership. Man, I have frickin butterflies now. I have no idea what a writing exercise interview even is... Not to mention, that they will also be calling my references. Now I have to figure out how to inform my 2 current Supervisors, who are on that list... Any ideas?
I would talk with the supervisors directly and tell them that you are just exploring options for your future. Tell them that you aren't necessarily looking to leave, but that as a responsible and ambitious person, you are always looking out for new opportunities to improve your options to provide for yourself and family. Reinforce that you have included them on your reference list because you believe that they are people that you can trust to honestly support you and provide an honest and unbiased reference for you.