Minor children as consenting witnesses

Hi All,

I am buying a self acquired property from a seller,  his family consists of wife and two kids (daughter and a son) both are minors.

Please advise if only wife is enough to sign as consenting witness on the sale deed or both wife and kids are required to be signed.

If kids are omitted, will there be any legal complications in the future.  

Note: This is a self acquired property by the seller.