We are Canadian and definitely not afraid of snow or cold weather. I learn to drive at 16 in mountains of snow, no issue with that. We will have a rental vehicle so not sure the chain thing is doable.
Sounds like unfortunately seeing Yosemite might not work out after all. We were already disappointed to find out our original plan to drive through the park on the way to Vegas wasn't going to work (you know. sort of rough triangle from LA to San Fran through Park to Vegas)...So we had hoped to manage a peak in the park but maybe another trip.