I think Doggy Daycare is a wonderful idea and one I wish we had here. Just from my own horrible experience I would say to have the vaccine done, but voice your concerns to your vet who may be able to adjust the dosage accordingly.
Things have changed in the last 10 years and makers of vaccines change too.
My own experiences were (just to bore you....) we had a beautiful GSD who thankfully had her kennel cough vaccine. We had to leave her in kennels one weekend to go to a family wedding. These kennels were virtually opposite my house and I knew the people who ran them very well. The kennels were immaculate and the dogs extremely well looked after. Teddy had her vaccine done about 2 weeks before we left her in the kennels and she was only there from the Friday night to the Sunday afternoon.
A week later, she started to cough and sneeze and was extremely poorly. She ended up in the Vets for almost a week with extremely bad kennel cough - so bad that if she hadn't been vaccinated we'd have almost certainly lost her
Unfortunately, there had been a dog in the kennels over the same weekend who had also come down with it and sadly he died
Several others all got it too - we never found out where it originated from as they would only ever take dogs that had been vaccinated so no one was to blame.
A few years after we lost our Ted, we had two 3/4 Persian kittens. They had all their vaccines and when they were about 9 mths old the Vets suggested trying something called Droplix for flea prevention. This was a vial that was dropped onto their necks - just like Frontline, Stronghold etc. Mine and a load of other cats almost died from it and it was withdrawn from the market, I do still use flea prevention drops though as things have improved.
I've spent most of my working life working with medicines and can almost guarantee you that any side effects will be short lived and usually well worth the risk as things vaccines prevent are very often far, far worse.
Also speaking from bitter experience, when I was a kid I wasn't allowed vaccines and neither was my brother (doctors wouldn't vaccinate as we had lung problems), hence I had every single childhood illness going (except Chickenpox)
I can still remember to this day, thinking I was going to die when I had whooping cough and so I decided that my kids would be vaccinated - and they have - against everything possible!!!!
The only reason I have used nosodes this year is because Charlie can't have vaccines because he's on other treatment and Maxx is now 7 and my Vet has agreed that every other year is more than enough for him.
I hope this might allay your fears a bit but it really is much better to get them vaccinated than get kennel cough. Sadly we lost Teddy when she was only five but her lungs never really recovered from the illness and left her immune system completely knackered