Looks like taking the train to Utrecht then taking a bus to the castle will take 2.5 hours. Any recommendations on a quicker way to get there (we are traveling with children ).
This journey should be possible within 1 hour (from Amsterdam CS).
I might be wrong but I don't think the bus between Utrecht CS and the castle is still operating. You should change train in Utrecht CS, to Vleuten station and then bus to the entrance of the castle.
Just use the planner https://9292.nl/en/planner
From: ... (No idea where your hotel is)
To: Kasteel De Haar, Haarzuilens