Just a note here...I agree with the comments above. However, even if you should have a heart to heart talk with these people, you must understand they think nothing of violating any religious preference you may instruct them about. e.g. "Please don't take my kids to meetings or read your literature to them." They would consider that God does require them to do so and they must obey God, not the children's parents. This also shows up when a JW has enough and quits, thus becoming an ex-JW. The JW's will attempt to show up for the children of the ex-JW, especially if said children were baptized. This is NOT OK.
I would also recommend talking to your children about why it is not OK for them to go to meetings and not OK to listen to the religious propaganda. But if the children are exposed to this indoctrination anyway, they may be encouraged to lie about it. And the JW's will further encourage them as your disapproval will be looked at as persecution (i.e. support that they are the "true religion.")