Complex sentence: Mixers allow dancers to meet new partners, the beginners have a chance to dance with more advanced dancers, and people may quickly assess dance skills of other persons without fear of being stuck with a poor match for the entire dance.
Split into simpler sentences: Mixers allow dancers to meet new partners and allow beginners to dance with more advanced dancers. Some people may take advantage of mixers to assess dance skills of other persons without fear of being stuck with a poor match for an entire dance.