Infants, toddlers, and children are fantastic opportunities for humor, symbolism, and character development for the older characters. Toddlers are rambunctious little scamps who are at the cusp of realizing that they are independent beings. They often oscillate between wanting freedom and wanting to rely on their caregivers. So, unless your toddler is completely self-reliant (which, realistically, they are not), she will always be involved with the other characters.
Toddler-hood tends to span between the ages of 12 and 36 months. There are a set of milestones [1,2,3] that children are typically expected to reach within this time period, but those goals are not always met. The growth and personality of a toddler will change multiple times between the ages of 12 and 36 months, and so will her cognitive, physical, social, and motor skills. Depending on the age range, your older characters could be dealing with a completely helpless child, or one who is able to run around and climb all of the dangerous objects. The toddler will require a lot of care and supervision regardless of her age, but the types of supervision will be different throughout her growth and development.
Having a mute toddler is an entirely different struggle. Toldder-hood is when children start being able to speak and communicate. Not being able to speak will lead to a lot of frustration on the toddler’s part. The parents of children who cannot speak for one reason or another often choose to teach their children sign language. This has been said to reduce frustration [1,2], although are very few formally reported sources. If your toddler is unable to communicate with her caretakers, this will be the cause of many tantrums. Since your toddlers also possesses powers, those tantrums could turn deadly in a moment’s time.
At the bare minimum, the older characters will need to help feed her, dress her, make sure she does not seriously injure herself, and provide social interaction. The level of interaction the older characters have with the toddler is completely up to you. The best way for the characters to interact with the toddler is by acting as her caretakers and guiding her through this frustrating period of her life.