LOR

Hi everyone,

I am in the process of applying to DNP at UIC in Chicago. One thing that confuses me are letters or recommendation. They want 3 letters to come from manager or someone in supervisory position. I have been working on my floor for a year. I do have a manager I was going to ask. I was thinking of asking a team leader as well but not sure if that qualifies as a “supervisory position.” For the third one, I was going to ask this coworker who was a charge nurse on my floor but is now a manager on the other floor and sometimes covers my floor as well. 
Does anyone know if these are actually good letters of recommendation? I literally don’t know anyone else who I could ask. Of course I know few doctors but they do not qualify I would think.