About waterproofing a circuit board
Ask you FR4 supplier about conformal coating options. They can mask it off, on the windows of the LED's and such. Check the water resistance of the LED's and such exposed parts. Most electronics are, as they are washed. Conformal Coating is very common on military and automotive electronics. A long time ago, I used it on video equipment that went in the trunk of vehicles to protect from salt build up from DEW point condensation.