What about next to your current mayor house? o: since it seems you'll have all your dreamies houses in one area, the other "residential area" would be your playing characters.
then it gives plentyyy of room southeast of your town for trees/pwps.
In one town I placed all 4 houses in a row. It gave me a lot of room at the top of the map.
You could put one near the dock if you plan on using that player as an island girl.
My main town 2nd player is close to the docks. She did all the bug hunting for the town after the mayor collected all the bugs/fish.