My 4 children are grown and it's a selling point for me because of all my practical experience over the years and that I can give all my attention to the daycare children because mine are grown. When you are advertising you don't have to mention that you don't have any children and you certainly don't have to tell anybody your reasons, that's your own private business. But at the interview stage with parents you should point out all of your experience with taking care of children because they will probably be wondering about that. And you can also let them know that you will be giving all your attention to the daycare children since you don't have any yet. Find your strengths and advertise them.
Good luck.