I've been many times throughout my life and it has always been pricey. That places takes an amazing amount of money and staff to run. I love it though, especially having been a few times and knowing where things are and knowing my way through the gardens.
How old are the kids? Some ages get in for free. 10-16, I believe. I don't think a kid younger than that would get anything out of a visit and no strollers or touching things in the house. I mean, it's a house, not a place that any kind of running and playing would be appropriate. The grounds would be fun for them. There is a petting area of the farm which I always like.