They cannot be good JW's if they maintain such a close relationship with non believers. Anyone not of the religion is considered a "bad associate" who can potentially "spoil useful habits"...
Your time together no doubt is counted as field service time, unless they are not really all that into the cult. As for your kids.....you can make it clear that you do not want them to teach them anything about religion, the bible, etc......that is your prerogative as parents.
Hope this situation doesn't go awry.....