Reddit mentions of Speedo Unisex Absorbent Sports Towel

You are probably correct. If the lessons are indoors, he will be warmer in just regular swim trunks and a swim diaper. Also, depending on the amount of interaction you are allowed to have with him during the lessons, you may want to get him one of those pool towels that divers use, like this one that he can keep by the side of the pool and dry off with when he has to get out. It's small enough that even if it falls in the water, it's not nearly as big a deal as having a huge beach towel fall in. I'm fairly sure they float as well.

Another suggestion would be seeing if rather than waiting on the pool deck, the kids could be allowed to wait in the water, hanging on to the side of the pool

I commuted to school a little over 12 miles during a month, my senior of high school so I know where you're coming from. I road a heavy mountain bike. I would first suggest getting a better fitting/appropriate bike, this will definitely decrease your time travel. Some other ideas:

• Get Sea to Summit Dry Towel or Speedo Towel
  
• Sick with some all natural deodorant
  
• If it is that bad bring a change of shirt/shoes
  
• Try to mix it up with Public Transportation
  
• Drink water
  
• Add panniers (No experience, but I have heard that it helps with back sweat)
  
• Enjoy your ride, take in surroundings, and smile
  

Just get a shammy

Speedo Sports Towel -Blue https://www.amazon.ca/dp/B000F6A9BY/ref=cm_sw_r_cp_api_i_1sZsDbHBHTPM4

Something like this