The one week of service is a rule of thumb in the corporate world for layoffs, and often dependent on the employee training their replacement, staying until a predetermined time (e.g., in event of a plant closure, merger) and in general doing a good job until they leave. Since nanny jobs are more transient and you often get more notice since it's obvious what age the kid is, it's not as standard practice. However, still nice to do it if you can and I think $1000 is great and quite generous for your situation.