We have child seats fitted onto unisex adult bikes, these generally take up to 20KG and are recommended for babies/small children that are able to support themselves and their head comfortably and confidently. A trailer can carry up to 40KG and has two small seats recommended for one or two small children able to support themselves and their head. A Tag-a-long is fitted to an adult bike and will take a child who can balance and feel safe cycling along behind.
All of these options are at the parent’s discretion.