From the airport to Royal Plaza Hotel, you can take bus E21 from the airport and stop at Tung Choi Street, Argyle Street. Then catch a taxi to the hotel. The cost may be around HKD20-25.
From the hotel to Disney Hollywood Hotel, you can take a taxi to Mongkok station, then take MTR to Lai King, transfer to Tung Chung line to Sunny Bay. You can take Disneyland resort from Sunny Bay to the Disneyland and walk to the hotel. The metro fare is about HKD21.
From Disney Hollywood hotel, you can take Disneyland resort to Sunny Bay, transforming to tung chung line to tung chung station. Then take the airport shuttle bus S1 to the airport. Well, since you have 3 kids and 2 pieces of luggage, you'd better catch a taxi from Disney Hollywood Hotel to the airport. The taxi fare is around HKD120.