General visitor rejected. Reapplying under family visitor

HI All,
I need some help here. Last year we wanted my parents in law to visit us and be with us for our first childs birth. Their general visitor visa got rejected.( Our TLR was expired and as our ILR application took nearly 1 year to process) Now we both have got ILR and our child is british. We visited them back home when our child became 4 months old. It has been nearly a year since they applied for the visa.
Now we would like them to visit us in the UK and planning apply under Family visitor visa. My father in law is now retired (Business has now been handed over to his son since he last applied for the visa) and they both receive nearly £750 a month jointley from rental properties(one property belongs to father in law and the other to mother in law, but the rental from both properties goes to the bank account which belongs to my mother in law). In the last application my mother in law mentioned that she is employed as a land lady(instead of saying unemployed with income from properties) and her monthly income is £750 (this is form both properties of which only one belongs to her). They dont pay income tax for this rental income.

I have transferred £2500 (money remitance receipt will be attached to the application) to their account last month to pay for there flight/etc.. I am sponsoring them for all their expenses. I have got a 3 bed house and more than £20,000 in savings (statements will be attached to the application). They have now got around £6000 in their bank including the money i sent them

My questions are,
1) Could you please let me know what I should mention in the covering letter, which supporting documents should be included, etc.. any sort of help/advice/opinion is appreciated.

2) Do we have to provide any documents for my father in laws business, even though he no longer deals with it?

3) Do we have to show tax documents for rental income (they dont have any as they haven't declaired this income to inland revenue , they do have renatl deeds, etc.. to prove this income and it get deposited to my mother in laws bank account every month).

4) What are the chances of them getting the family visitor visa?

5) what are the differences between general / family visitor visa?

Thank you all in advanced

Any one?? Any comment??

My In laws visa has been rejected twice on the similar basis. Second time the ECO ignored the proofs of income completely and rejected based on single transaction in bank account.
I have since applied for Judicial Review and it is currently under process. Hopefully i will get som positive results from there.

Also I have started the petition for bringing the appeal back as quality of these decisions made by ECO's is so poor. Sign it and get your friends to sign it so that we can fight against bad decision like this

Hello!
I've started the petition "Theresa May, UK Government: Bring back the right of appeal for family visit visas" and need your help to get it off the ground.
Will you take 30 seconds to sign it right now? Here's the link:
http://www.change.org/p/theresa-may-uk- ... isit-visas