When I recently submitted my application for a visitor's visa to the UK for a 2 week holiday for my wife, daughter and niece I provided copies of the email booking confirmation for 2 night's hotel accommodation for when we arrive and just gave my folks name, address and telephone and email number. In the itinerary I said we'd be visiting them and then touring around shopping and sightseeing. I didn't provide any other proof besides the initial hotel accommodation booking confirmation and it must have satisfied them as we got the visas no problem.

Just to update the wife's application,,,, today 17 days after submitting the docs, she recieved a 5 year multi entry visitor visa in the post,,

she has no registered business or work, so to support her need to return so instead she submitted my travel details showing my flight boarding passes departing from BKK airport to my work location at regular intervals over the past 3 years,, also letter from our kids school granting them permission to take time off for the intended holiday additionally mentioning that she had never overstayed on previous visits and never applied for settlement suggesting that her visa requirement was purely for visit purposes,

In other supporting docs she also submitted letters from my son and daughter in uk,, my mother (who we will be staying with) and also good luck on your visa application mails that my sister and brother sent her were also submitted,,

Joint and her personal bank acc in Thailand recently updated, entry exit stamps in our passports of previous visits together to other Asian countries over the last couple years submitted,, support letter from me, letter from my employer, and other stuff confirming the strength of our relationship

Now thankfully we won't have to worry about the hassle of it all for another 5 years