Super nice covered porch area to use! And what a charming pond area. Congrats on the house. So many ideas.
Do you have fish in the pond? If not, there are floating misters with strictly blue lights (not the rotating LED color show) made for ponds you could use for some effects coming off that area.
The boat with the pond nearby definitely are tingling some brain cells. River Styx theme with reaper, skeletons, Greek themed props; Egyptian River of the Dead with ancient Egyptian props; something more recent like themes from movies like Lake Placid or Camp Crystal Lake from Friday the 13th. Maybe the house could be made into a cabin on the lake. Floating gators or ones sitting on the bank would definitely fit in.
Is your hot tub in use or is it drained right now? If filled it could create some nice rising steam to build a theme around. And if it has lights inside you could try attaching colored light covers to them for more mood setting. How about turning the hot tub into a volcano, add red light covers inside and drape brown tarps over the sides to create the slope of the volcano. Turn the general area into a jungle with head hunters, diamonds and other jewels, snakes, spiders, etc. Maybe the natives threaten to capture ToTers and serve them up to the gods of the volcano.
I'll give it some more thought but can't wait to see what others suggest.