Severance pay.

I have been a loving weekend nanny (3 days per week) for a family with 2 children for 8 years. My position was "on-call" on the weekends from Friday through Sunday and the pay was very good. They are now letting me go, but for reasons that have nothing to do with my performance. I am wondering what would be considered good severance pay considering my length of employment and the commitment and dedication I've show to this family over the years. I started when their children were in diapers and drinking from bottles, so clearly I have a long history with the children and a very nice relationship with them. My job is a kind of a niche, and it will be very hard to find something with similar days/hours and with similar pay. What do you think is fair/appropriate for my severance pay from a family to whom money is no issue at all??? Thank you!