Children younger than age 2 need not wear masks. While walking outdoors, as long as children can maintain social distancing of more than 6 feet and do not touch tables, playground equipment or other things that infected people might have touched, then they will not acquire the infection and would not need masks.
Next Steps
If you must go outside or to a place where you are not able to practice social distancing with an infant, cover the infant carrier with a blanket, which helps protect the baby, but still gives them the ability to breathe comfortably.