A child with Thrush or a yeast infection diaper rash can absolutely still go to child care, there is no need to keep them away. Remember that every has some candida in them and this is not some contagious infection they will pass on by just touching others. It is an overgrowth of an organism already in them. As long as they seem up to child care, i.e. they are not overly in pain or discomfort, that can attend.
Since it is possible for the yeast to be on pacifiers or nipples of bottles occasionally, just have the child-care provider keep to good hygiene practices, don’t share the child’s pacifier or nipples with another child and boil them after use. Wash hands if coming into contact with a lot of nasal or oral secretions if they have Thrush. Wash hands after changing their diaper.