The last 's' in terms of a sequence

From a song I've been listening to, written and performed by Keith Green, here is a logically loaded construction. I want more than Sundays and Wednesday nights. This is a song criticizing Christians for limiting their dedication to God merely to their meetings at church, which in the Protestant churches is on Sundays and Wednesday nights. It is easy to convey the wrong times though by eliminating the 's' on Sundays. Then it becomes Sunday nights and Wednesday nights, which was not the intention.

• Sunday and Wednesday nights = Sunday nights and Wednesday nights
  
• Sundays and Wednesday nights = Sundays (sometime during the day or all day long and Wednesday nights)

Be careful of sequences and the final 's' on the terms!