Hi Justin,
I don't think you are setting a bad example at all by being a bit relaxed on the first class meeting. I have students coming in at various times because they are trying to find the right room, etc. Being a little lax on this first class meeting shows you have an understanding of their trying to find where they need to be.
I make it very clear that I enforce a strict attendance and tardy policy. The policy is explained in the syllabus and in class. I don't have a problem with the students after the first… >>>