I found these great Everyday food and Sometimes food cards at Montessori Nature.
This would be a nice activity to do one on one initially and then as the child grows confident they cn do it on there own. There are quite a few cards so for the 3 year olds I would be tempted to take 4 cards (or more) from each category and then you can change them around to keep it interesting.
This activity would spark some lovely conversations with lots f opportunity for connection. It could even lead to some preparation or cooking experiences!