Ahoy, Tatiana! Welcome back to planDisney and thanks for sailing over with your Disney Cruise Line question.
Unfortunately, the
Terms and Conditions for Residents of the United States sailing with Disney Cruise Line prohibit the type of stateroom arrangement that you are proposing. Minors under the age of 18 must either share a stateroom with a parent or legal guardian and/or be accompanied by an adult 21 years of age or older staying within the same stateroom. Since your son will only be 20 years old at the time of sailing, you will not be able to book a stateroom for him and his two sisters.
I know that is not the answer you were hoping for, but let me suggest two ways to potentially solve your problem: (1) if you change your sailing dates to after your son turns 21, then the connecting stateroom configuration you proposed would work for your family; or (2) you can book a single stateroom that is large enough to accommodate your entire party of six, so that you can be in the same stateroom as all of your children.
The exact stateroom offerings will vary by ship, but only the concierge category will have rooms that can accommodate your entire party of six within a single stateroom. You can view the stateroom configurations for each ship
here and see which options may be available.
I hope you are able to find a solution that works, so that your entire family can enjoy sailing where magic meets the sea. If you have any other questions, then you are always welcome at
planDisney. Happy sailing!
Catherine