A few extra co-pays for peace of mind

OK, my poor little guy is going through his 5-year-old vaccine boosters. And I'm dragging it out. But I once heard a heartbreaking story about a child who died shortly after receiving all the shots in a single day, and our pediatrician understands my nervousness and is very pleasant about my breaking it up into separate visits. So the little guy went once last week, once again today, and he's still needs his MMR booster so we'll go for that in about a week. Each time I have to pay a new co-pay for an office visit, but I don't care. That story has always haunted me, but I recall how impressed I was with the mom, as devastated as she was, saying she's not against inoculating kids, but she advocated for not doing all the shots at once. Each time my kids got to this age, I insisted on breaking them up.
I know that was really a fluke thing that happened, and kids get shots all the time, but for my own peace of mind, I bring them for a second or third visit, depending on how many they need.
But I feel bad for my son. "I don't want a shot!" he said as we pulled in today, last week's needle probably fresh in his mind, although he didn't cry either time. "You're almost through with them." I hate to tell him he has to go back there once more. I'm going to have to do some serious bribery.