Baby Sitting Service.....................?????????

Me and My Friend are both ages 11-13.We are making a baby sitting service for the summer.The ages are 1-7 years old.Should we use these prices $15 1-4 years old a day $18 5-7 years old a day.Also our hours are 7am-5pm Monday -Friday.A $5 late fee for every fifteen minutes.It will be at my friends house.And, we will tutor for an extra $10 a week.Snacks and lunch are an extra $4.Or they may bring their lunches and snacks.It will be June 9th-August 15th.I added all the profits and we should make about $6,000-$7,000 i think without splitting it yet.The limit of kids is 12 kids a day.Please help and correct any of our mistakes or put more ideas and tell us if we should do it or not.