I think it would depend on what the intention of having this policy is in the first place?

The intention of my late fee policy is A) make it clear I do not WANT to work late because I have a life after work and already work a long day as is and well I find it rude if someone does not respect my time by ensuring that they are here on time and B) I want to make sure that I am well compensated for overtime if someone does make me work late and C) make it clear that chronic lateness will result in termination of the contract regardless of if they are paying me a late fee .... so my policy is written that late fees are charged per child still in attendance I do not do a 'family rate' for anything ~ fees are fees and are based on per child in attendance.

IME some people if you do not charge enough to make it FINANCIALLY STING to be late they will just consistently BE LATE and pay the fee and think nothing of it ~ they almost start to feel 'entitled' to be late because they are paying the fee .... when I worked in centre care we use to constantly have people come in laughing and waving their late fee like it was a bloody tip cause they lost track of time at the gym or stopped at the grocery store on the way home and they could care less that we were inconvenienced at having to stay and work late or that we might now be late ourselves to extra curricular activities or picking up our own children and so forth.

My motto is just BE ON TIME and we will not have any problems