Net result: he and I came down with it on the same day!
For Matthew (about 5) and Rachael (about 8), it was a fairly mild deal, no lasting scars that I know of.
For me, I was about as sick as I've ever been, absolutely miserable, feverish, mildly delusional (yes, more than usual), and pain-wracked — and it was the first day of a week in the mountains for Valerie and me! The local doc recommended sweating, and Aspirin. I took Aspirin, and went out to our car wearing a coat and rolling up the windows in 100-plus summer heat, because I felt so terribly guilty for wrecking my wife's vacation. She (a totally great sport about it) came out and dragged me back inside, and we watched the '92 GOP convention, then eventually went home early where prescription painkiller gave me my first moments of comfort. (We went back a few weeks later and had some fun!)
I'd say get the vaccination or get it over in childhood. You don't want to be adult, and have CP.
Dan