I thin you made a great choice-Poly is very romantic & relaxing. It does attract families because it's on the monorail, but no more than the other monorail resorts. You will find plenty of couples there as well & it's a big enough resort that you are not going to feel like you are in romper room or something
Romance-wise, you cannot go wrong with most of the resorts IMHO, except the Values. It all depends on what type of theme you consider romantic though.
Romantic perks about the Poly:
-White sandy beaches with Wishes viewing (and music piped in) & also great view of the Electric Water Parade
-Beautiful MK castle view
-You can take a boat to the MK
-Gorgeous & relaxing lobby
-Exotic flowers & foliage throughout. Fire lit torches to guide your way
-Beautiful & comfy rooms
-Awesome bar/lounge with fantastic entertainment
-Deluxe, so you get great service overall
-You can order in-room private dining if you would prefer
-On site luau show
-You are garunteed to get lei'd!

(Sorry, I couldn't resist!)