One of the first things I made for 'Bella when her Mom, Lea, needed an extra layer put on as fall arrived and worked well while 'Bella rode in her sling.
It worked equally well to pop on riding in the stroller, because it opens flat, it can be used as an extra blanket.
As 'Bella became a toddler it was obvious how wonderful her ponchos were as she was/is definitely an "I can (and will) do it myself" young lady".
Without sleeves, buttons, or zippers, she could put it on and be ready to go.
A poncho can also make a dramatic statement for a five or six year old!