I'd stand there, not looking in their direction. Pretend I don't
  notice them.

  Then they can make the first move.
  My original intention for doing so, is how I deal with strange
  children I have to deal with for some reason and quickly gain
  their confidence, animals I don't know, and adults whose
  intentions I don't know but might be hostile, might not be.

  I just do whatever I'm doing, not noticing, but occasionally
  glancing so they know I'm noticing a little.

  This way it gives them space to look me over, check me out,
  smell the air around me, decide what THEY want to do and how
  they want to approach me.

  When they indicate their interest in engagement, then I will
  engage but slowly, just a little bit at a time.

  Mind you, I don't know HOW the aliens might engage.

  I don't know if they have amygdalas with fear type components
  that I need to be aware of.

  But it's all i have to work with at the moment that I know works
  among life forms on earth