What to charge?

[gini]

I charge a flat summer rate, but have a 6 year old attending 4 hours of summer school a day, which she started on Wednesday of this week. This is also her last week with me along with her brother. The parents have been hinting about what they will owe due to the girl attending summer school (which was also not mandatory, but choice of parents) should I charge a special rate because of summer school? Also, today (Wednesday) in the morning they advised me the girl wouldn't even be coming to daycare only their son, then they arrived 35 minutes late to pick him up (it was before my closing time, but later than he had told me that morning that he would be picked up). Should I stick with the flat summer rate or alter it?? Help!!
Gini