Duration
Hi BR2004,
I agree with the all suggestions of mdu123, except for the duration of stay, which he says put for 6 months. I will strongly advice you to put the duration of stay, for less number of minths, say 2 months or so. This is so because your mom is still working and it is hard to justify 6 months leave. The consulate may ask why does your mom, working as a govt. employee, is taking 6 months leave ?
See the intention here is to prove that they will be visiting for a temporary duration, and they have every intention to come back. The job is a good reason to want to come back. But taking a six months lave from a job, may seem like she is not concerned about the job. Imagine yourself in their shows. When you go for a vacation/visit do you take 6 months leave, will any job allow 6 months leave ?
Even if you put 2 months, this will not affect the duration of there say in US. They can still come and stay for 6 monnths, as that duration is dependent on the duration put on their i-94 at POE. At this point your main concern should be of getting them a visa.
These are just my suggestions. It is upto you to decide what is best in your situation.
setra2002