Part time and after school care

I have decided to start doing part time and before and after school. But I am just confused about a few things and I am wondering how you all do it.

Part time:
In November, I will have two part timers; one does mon,tues,wed, the other does wed,thurs,fri. I'm wondering about stat days. I am thinking if the stat fell on the Monday, I would charge only the one coming on the Monday, right? How do you all handle part time and stat holidays?

Before and after school:
stat holidays...charge?
PD days, March Break - charge full day fees?
how much do you charge for ONLY after school?

Any other information you can give me about after school care? This is usually my calmest part of the day; the kids get up between 3:30 and 4, snack and play until parents pick up. Now, I will be picking up a 7 year old at the bus at 3:30, snack, and play? But My second oldest is going to be 3 in October so they're close in age, and I don't have a lot of toys. My husband suggested I hook up the Wii, but I don't know if I'm keen on that. I can do outside play, but I am worried about the winter and colder weather. Do 7 years olds require a lot of attention or can they pretty much entertain themselves? Is it appropriate to get him to do his homework?
Anything else...as much info as possible please!!! :) I have the interview on Tuesday and I don't want to seem like I don't know what I am doing :)

I'm also assuming I'm going to have to do up a whole different contract, any suggestions for that as well?

I've just started doing before/after care as well. I do charge for stat holidays, and for PA days and March Break I charge the full day fee. For only after school I charge $12/day/child. And yes, I changed my contract for clients who are doing before/after care. As for homework, I ask the parents if they would like their children to work on it here or wait until they get home. I let them know I am willing to help the kids with homework, but I make sure they know it's not a guarantee--I am busy with other kids too!