I recently sent WDW Reservations an inquiry about connecting rooms. Attached is the email response that I received. In general terms, if the children are young, you should get connecting rooms.
=== Beginning of attached email ===
Thank you for contacting the Walt Disney World® Resort.
We can certainly appreciate your desire to assure connecting rooms for your party, however it is a request which cannot be guaranteed.
Such guarantees are made only for families with small children who must be in a connecting room due to the party size or other reasons. Since all rooms cannot connect, these parties must be
accommodated first by reason of the safety, security, and well being of small children in the party.
We have placed a request for connecting rooms on your reservation which will be honored by the hotel if possible. We have also included a notation to front desk cast member stating your strong desire to have your request honored. Once again though, we must restate that while resort cast members will do all in their power to accommodate your request - it cannot be guaranteed.
Under any circumstances, connecting rooms will be assigned to parties with small children on a priority basis.