3 Questions for business-to-consumer setup

3 Questions for business-to-consumer setup

CONTACT and ACCOUNT Relationships
1) We are primarily a business-to-consumer company (we are a school and our product is classes). Many of our customers are the children in families. If SON is our "account" (he's our student), we would list his MOTHER and FATHER as contacts on his account. But what if we then add DAUGHTER as a student, or even lets say that MOTHER also becomes a student. How do you suggest we deal with this inter-relationship? I've thought about making the family name the account, though we have many families with the same name, and it is possible that members of a given family will actually be a part of 2 families, so that doesn't really work. What is your suggestion? It would be very nice to be able to associate a contact with multiple accounts, and/or be able to turn make one account a contact of another person. Or even if I'm using contacts only, to be able to make one contact and contact relationship of another. Is there a way we can do this?

SERVICE PRODUCTS
2) We offer service products. How do we specify this in the product page so that it doesn't keep indicating an out of stock problem? We don't really have a seat limit, so making the stock the number of seats in the class isn't necessary.

IMPORTING SALES
3) We are importing from an excel spreadsheet. Right now, the classes that our previous students have taken are listed by column in the spreadsheet. How do I import those classes they have taken to reflect it correctly in Zoho? Should they be listed as invoices? Isn't there an easy way to just "check box" classes that they have taken right on their account/contact page? Or is it necessary to create a whole invoice? And should it be an invoice or a sales order?

Any advice would be GREATLY appreciated.

Thank you!