I do have late fees in my contract, but am also pretty clear that it in no way condones being late. Here's my late pickup section of my contract:

Late Pick Up

XXXXXXX is a home daycare, and as such, we have family activities and obligations after daycare hours. Please respect our family's time. Many children become anxious when parents do not arrive at their usual time. Drop offs and pick ups must be made at the agreed upon times each day unless other arrangements have been made in advance.

Late pick ups (after the usual time without prior arrangement, or after closing) will result in additional fees of $1 / minute after a 5 minute grace period.

If the unexpected arises (traffic, bad weather, etc.), please call to inform me that you are running late. You will be charged an extra $5 for the first 20 minutes, and $1 / minute after these 20 minutes.

Late pick up fees must be paid before the child may return to care.

Habitual lateness may result in termination of care.