model lady started following Transporation to/from the pier and Hong Kong Disney
Ocean Terminal is near to TST station, bit of a walk with a 3 yo. The station you want for Disneyland line is Kowloon. Take a taxi there with your group and then 5 stations to Sunny Bay and then on the Disney train for 1 stop. There used to be a fireworks show every evening and there is a grand parade in the afternoons. Maybe time your visit to fit these activities. There is plenty to occupy the day, so long as the 3 yo can last. Have fun.