IMHO, you are betting off using something small, cheap, waterproof, and designed for boats than you are using an iPAD.
I used to have a Lowrance 3.5" color GPS unit that came with high quality charts and a fishfinder / depthfinder. They still make a similar unit, the Lowrance Elite 4:
Elite-4 - LOWRANCE | Marine Electronics
It costs around $300.
For wind display you will need to purchase a separate unit. A less expensive unit, like from Moor Electronics
is around $400.