You're in a very precarious position. However, even I, a mere woman and never "head" of anyone, would insist that I have a stake in what my own children are being taught. Anything less would be child neglect, IMHO.
The most important thing to remember is that your children need to feel secure and accepted by you. You need to keep a sense of humor and a lighthearted approach to countering the hate literature they may be forced to read or listen to being read. They will not remember details and facts as much as how they feel when they are around you. If you need to talk with a counselor about how to handle the situation, you will be well advised to do so. This is about the best interests of your children, not a power struggle between you and the WT (although the latter cannot entirely be ignored).
Wishing you wisdom and advising caution,
SandraC