Babies and Toddlers can safely sleep with a pacifier in their mouth all night.
Pacifiers have breathing holes built into them so that the baby can breathe and actually pacifier use at night can even reduce the risk of SIDS in young babies.
So if your baby wants to sleep with a pacifier in it's mouth you can safely let the baby or toddler do so.
Toddlers should be off a pacifier by age 4 at the latest but allowing them to sleep at night with the pacifier can help your toddler or baby drift off to sleep and comfort them.
Many babies and toddlers sleep just fine with pacifiers and are okay.