Here are things to think about...
- As stated, aft rooms should be avoided on the Fantasy at all costs, especially those within about a half dozen doors forward or aft of the aft elevator area - these are prone to SIGNIFICANT vibration issues (ask me how I know...lol).
- Deck 10 is the highest deck with staterooms. Deck 11 is where Cabanas is and the pools are. Cabanas is aft, pools are mid-ship, and forward is where the quick service restaurants and adult areas are.
- Main Dining Rooms are mid-ship (Royal Court and Enchanted Garden) and aft (Anamiator's Palate).
- Theaters are forward.
- Mid-ship elevators are the most congested "in general".
- Most characters greets are mid-ship with some being forward on Decks 3 and 4.
- The adults section with bars and lounges is aft.
- The adults only dining is aft.
- Kid's clubs and such are mid-ship / aft.
- Shopping is mid-ship.
- Deck 2 is lowest passenger deck and is where Enchanted Garden is located.
- Starboard side would allow viewing of fireworks from your verandah.
- Starboard side seems to be the more common side to be able to view
Castaway Cay from your verandah when docking (the ships tend to back in more often than nose in when docking).
Now, with all of that said in terms of how to get where... It's a really big ship, but you can navigate it pretty easily. I had an aft room that was "uninhabitable" and got moved to a forward room (both on high decks). Neither of them felt further away from things than the other.
Personally, I like the higher decks when you have a verandah because the view tends to feel "less obstructed". I do not seem have issues with motion as it has never made me ill (even in rougher seas on my 2014 cruise in early December on the Dream), so the higher decks work for me.
Be mindful of what's directly above you if you book Deck 10 - the pool areas will make noise as they set up the loungers at the start of the day. Some have had noise from Cabanas in the mornings, but that hasn't been my experience. On the Dream / Fantasy, Deck 9 seems to be a good compromise for me as it's high up but not directly below a deck area where there's activity.
Avoid a room that's directly visible or within a couple of doors of an elevator access area as these are the most likely to have extra noise from foot traffic. In fact, a forward room that's a few doors forward of the access area will tend to have the lowest foot traffic overall in front of your room... We really like 9526 on the Fantasy (wont' work for you as it only sleeps 4) because it was SUPER quiet in that area (and the laundry was a one minute walk forward of our room along our hallway).