Freed0mAndTruth

I believe no information should be withheld. However, I think you shouldn't be telling them things they can't understand. For example, "Where do babies come from?" From mom's tummy and leave it at that. If they are older and they ask how do they get there, you can tell them that dad puts it in there when mom is ready. As they get older they'll naturally learn more and ask more, but they'll never have to unlearn anything you told them. They'll also appreciate it that you didn't lie or talk down to them by saying things like "we'll tell you when you get older."

I feel like when you have a one-on-one situation with a person of the opposite sex, there is always some sexual tension / feelings involved. If she is happily married with kids, this is usually not a problem as those feelings tend to be motherly. However, in your situation, it will eventually evolve into something. And it'll probably not be something good. Don't wait for things to happen. Take action, go find another therapist.