Visa application certification questions

Hi all,

Just trying to prepare for a visa application for short holiday (few weeks) to Australia. 

Applicant is in Koh Samui.

Has right now about 80,000 baht in savings probably closer to 90,000-100,000 upon application. 
Will write a letter inviting and hosted accommodation picture of house and ownership proof.

My pay slips.

Have applicants birth certificate, have ID/license of applicant and parents and daughter for proof about family. Reason to return.

1st question

For proof of family is the id card front and back and a bill or rent slip with name and address good enough for family proof?

2nd question. 

The bank statement is in english but part thai. i.e. balance etc can be read in english. Is it best just to print the thai one and pay to translate it anyway? 

3rd question.

After getting translation done they need to be certified. I am assuming a doctor or other professional can certify both the translation and originals? 

4th question. 
Is the biometrics mandatory?

I was going to try application online. Since it is hard for applicant to travel to bangkok just to submit application. 

the wording is vague for online process. 
If has to be done then it has to be done but if they skip it and do upon entry in Australia that would be good. 

5th question

I gave a template for her employer to follow to advise of return to work is possible in english. 
They will apply to their letter head. 

I assume it is ok in English. the employer can speak some basic English.

Anything that is good to know is welcomed. 

Thanks,