Whenever I have an issue that needs to be addressed with one or more parents, I usually like to write a letter to everyone. That way, the conversation can be limited if there is no time at pick-up but they all still get the same information. It's also sometimes easier because no one is "put on the spot."
If you haven't done it already, maybe something like this,
Dear parents,
This has been such a wonderful month since I opened my daycare. It has been just a flurry of activity here. With all of this new excitement however, I believe an issue may have been overlooked.
It is very important that your children eat something before coming to daycare. My schedule does not allow me to provide breakfast and we don't have morning snack until 10:15. I am afraid if your child has not had anything to eat when they arrive, they will not be able to fully enjoy their morning activities.
Thank you very much for your cooperation,
I also think it is a good idea to have this conversation or letter for all parents because, in the future the child who has had breakfast now, might be the one who comes without eating next month. This way, everyone is on the same page.
Do you have a policy about bringing the food into your house? If not, consider one. I have had children walk in at 7:00am with a baggie of chips, cheesies, and even a pizza pocket! "But she just found it in the car..." NO! Any parent who has allowed this has seen me take it out of their child's hand and put it straight into the garbage. I am guessing it's just because they want me to be "the bad guy." Happy to oblige. My policies are in place for a reason.