Hi, welcome to the forum.
Before you let kids come into contact with JW relatives you must teach them how to think. There are books on how to do this, and they may benefit you as well. E.g. 'Teach Your Child How To Think' by Edward de Bono
You must also teach them how to recognise the warning signs of mind control. Unfortunately, there seems to be very little available that is suitable for young ones. If anyone knows of any good books on the subject, please start a thread and list them.
You could start by familiarising yourself with these techniques so that you can explain them to your daughter in language that she can understand. If she starts chalenging some of your own pet beliefs, you have succeeded, don't spoil it by bullying her into accepting your views.
Armed with the above, she should be quite safe with relatives and school friends who are members of any of the high control cults.
Cheers
Chris