If something happens to your child whose fault is it? The adult, the older child. How can you qualify that an older child is able to 'help' and in what capacity.
My mother in law runs an in home daycare. Has been for over 25 years. Fully licensed. The rules and regulations get harder every year. She is allowed 8 kids at most at one time. She has to be certified in CPR for children and newborns, take continuing education courses, background check anybody who lives in her house (including herself) since she runs an in home daycare, monthly/quarterly/random visits from the state, and stay on top of all of the various new rules.
While it has worked in the past, I just can not see it working in our current sue happy culture.