Welcome Aboard, Abigail!
How exciting to be planning your FIRST Disney Cruise Line Vacation! I remember how excited I was when I was planning my first.
I would agree that a stateroom located midship is the best option to avoid motion sickness. I prefer to be midship as well, just because I like to be centrally located. If all of the rooms that you are looking at are booked, have you considered two connecting staterooms? These rooms have a door between them, and are ideal for families of 5. This would also give you an additional bathroom, which is always appreciated in our family! You can book two Inside Staterooms that connect, or splurge on two Deluxe Oceanview Staterooms with Verandahs that connect.
When booking a stateroom, I try to find a room that is "sandwiched" between other staterooms as well. This means that both above and below my stateroom are other guest staterooms. I made the mistake one time (on a different cruise line) of booking a room that was directly below the pool deck. The crew members started moving deck chairs around at 5am, making sleep impossible. Our favorite deck on the Disney Magic and Disney Wonder is deck 7. If you are stopping at
Castaway Cay, try to book a stateroom on the starboard side (right to us non-sailors), to get a great view of Disney's private island paradise from your stateroom.
I wish you all the best of luck planning. I will look forward to you asking more questions as your cruise gets closer. I had TONS of questions before my first cruise!
Happy Cruising, Tracy V.