Children visiting visa for my niece

Hi ,

3 years back i applied for visiting visa for my sister and brother- in- law, and they got there visa ,and now i want to aply for my niece who is 1 yr old. My question is can i apply in Interview weiver program ?and if they want to go for inperson interview will they allow both my sister and brother-in-law for interview?and how much amount do i need to show as my bank balance ?if they are sponsering by themselves how much they need to show liquid + fixed deposit?

For 1 yr old niece, it will be a drop box case.Nobody needs visit to consulate.

website gives list of documents and procedure. Normally child will be granted visa based on parents visa