Interesting start though Daphne seems a little to trusting/nice? for a Slytherin.
For Harry consider a thestral. Can fly. Invisible to most his friends but not most of his enemies. And not a snake. In fact more reminiscent of a deer.
For Daphne a small grass snake.
No Ron/Hermione/Others?
I don't particularly care for stories where Harry is Uber-Powerful. Any great power really should have a not insignificant downside to keep things interesting.
Also instead of Harry being a super genius learning new skills consider him finding artifacts that grant him power(without him knowing all that they do).
Harry has always struck me as dumb but powerful.