Family visitor visa questions

I'm a British citizen, and my wife is Turkish, and has recently received her ILR. We'd like to have her parents visit us for 3 weeks in Spring, and we're currently working on their applications forms for family visitor visas. I've got a few questions about the documentation that needs to be provided:

1. My in-laws plan to stay with us, and they'll provide their own money for trips and stuff like that. Does that mean I don't have to provide my own financial information with the application as we won't be supporting them?

2. What do I need to provide to prove we have enough room to accomodate them?

3. My father-in-law took out a large amount of money from his bank account about a year ago, but hasn't used it for anything. My concern is if he deposits it into his account now it'll look very odd. Is their anyway to explain the situation?

4. My in-law don't know the specific month or day their parents were born, is it okay if I just put the 1st of Jan for their birthdays?

5. My in-laws have two homes in Turkey, one in Istanbul and one in Datca, will they need to provide documentation proving their ownership of both properties? Rather then original copies can they send certified copies instead?

6. Will all documents need to be translated into English as well?

7. Will they need to write a letter explaining their various ties to Turkey, and would that need to be translated from Turkish to English? Or could I write the letter in English and have them sign it?

8. When we write the invitation letter will it have to in Turkish as they don't speak much English, or would it be okay to do the letter in English?

Many thanks for your help.