I have seen a case get rejected where a couple was married for 10 years with 2 kids!S.K said:You are not required to provide proof of recent contacts as these documents are asked to see whether the marriage is genuine or is a marriage of convenience.
In your case you already have 3 kids so you should not worry to prove that your marriage is genuine.
Rules have completely changed from what they were 2-3 years ago, I suggest you do follow the guidlines of new procedures, you might not need to provide as much proof as the newly weds but definately some family pictures, and money transfer receitps, phone call logs should should do it.