I’m completely in agreement with you on this one. I don’t like the idea of people accosting people who have otherwise shown no interest and bothering them about religion. I particularly dislike this amongst Hindus, because, to me anyway, it seems to violate the basic ethos of Hinduism, that each person is free to seek his or her own path and that “truth” is not owned by any one person or group.
By the same token, whether or not to go around witnessing is one of those choices you’re free to make, though.
Plus, they’re the harmless sort of preachy people; unlike, say, (many) evangelical Christians or fundamentalist Muslims, they aren’t trying to make their worldview the law.
My mom (a high school English teacher) organizes trips for fellow teachers and students to visit places of worship as an educational experience. While she has a relationship with most of the leaders now, she started by just calling them, and asking if they would be willing to talk to the group. All of them were very eager to help, and the visitors genuinely seem to appreciate the experience.
I would call or shoot them an e-mail to ask when you could come by for a visit. It also might be a good idea to ask your daughter’s teachers if they would like to involve her whole class.
Heh. I have asked me if I’d like to involve the whole class, and I answered yes, so we will all be going–both kids. 
Sorry, we homeschool, not that you were to know.