Oh, you don't want to fulfill it. The Hidden Agenda is like what makes us tick. Without it... we've pretty much got nothing to live for. Just let your INFps keep groping out into the void that is humanity itself and occasionally your breasts (I didn't just say that to a 15-year-old girl).
EDIT: Now that I think about it, you can help them by making sure the following things are always nearby: a computer with fast internet access, lots of books with a library and big book store nearby, a park, a television, and lots of conversation pieces.