Can H4 travel before 2months of expiry

Looking for input for below situation

My visa is going to be expired on 1st APR 2017 and am planning to get my wife and son here and then start the extension process as my employer will do normal processing only and i do not want them to block in India till i get the new visa

  1. will there be any issue for my wife and son for stamping for current visa ?

  2. will there by any problem, if they travel in between 2nd week of Jan and then i file the extension once they come

  3. what documents needs to carry for the stamping ?

  4. any questions that will be asked specifically on visa during their port of entry and documents that needs to be carried

appreciate your help here