Hello T..
I am a working mom to 3 children (Boy 15, Girl 13, Boy 5) and I've had my share of "illnesses".
As for "swimmer's ear" prevention, there are some drops sold everywhere (they're cheaper at wal-mart) called "swim ear"...these are God sent and they work just great, I promise! The drops can be administered after swimming or after a bath...it just takes a few drops (read instructions). My two older children went through some major swimmer's ear when we first moved to Florida (12 yrs. ago) due to swimming lessons...the doctor recommended these, I make sure to keep a few bottles of these in my medicine cabinet and I will say that I use them regularly on my youngest - he loves to swim. My older kids know to administer the drops after swimming or when they get water in their ear(s) after a shower. I promise you that they work great!
I didn't have any tonsil issues, but the coughing was one thing that always stressed me out, especially at night. Here's what I did to help them with their cough during the night...a circulated email at work came through my computer one day indicating that rubbing "Vicks Vapor Rub" on their feed and putting socks on them when they go to bed helped to stop the cough and it allowed them (and the parents) to have a good night's rest. Well, I tried it and IT WORKS!!! I did some research on it in the internet and I only found positive information about it. And, of course, after seeing the results for myself, I totally suggest that you try this with your daughter before going to bed.
I'm sorry I don't have experience with the "tonsils" issue, but going to the ENT is a smart thing to do.
Well, good luck and I hope that all goes well.