It has crossed the line:

1) Obviously the motives of the creators of the exhibit are suspect - they're christian men who have produced this exhibit for religious reasons.

2) the mention of truthfulness - a properly nuanced discussion of this is way beyond junior school. Given 1) above I strongly suspect the answer will be unequivocally - yes, it's all true!

3) the mention of the "message" - again, do we really believe this will be presented in a "this is what xtians believe" way, rather than - this is the message and it's true.

4) the gospel of John gift. "During this time over 600 000 children have experienced the Exhibition, read God’s word for themselves and all received a copy of John’s Gospel away with them."

I do think, by the sounds of it, your daughter is up to the challenge of this event, however it does go way beyond religious education into religious indoctrination.