You really want to keep the 'coons from patterning on your property. Moms learn where the food is, and the little ones follow her. Then when they have their little ones, they follow her. Break that cycle when you see it. They are a pest in the city because their only predators are cars. Toronto has big problems with the little christers breaking into supposedly animal proof compost bins.
As for diseases, they are a known vector for rabies. You'll have to check out the provincial distribution maps to see how much risk you have to consider.
As for taking up residence, don't let them den up anywhere! Their turds are not necessarily toxic like radioactive waste, but if they are carrying diseases, you're at risk. The bigger issue is their destructiveness. They get in the attic and will make a mess you'll have a hard time cleaning.