Which fish finder / gps

[Ddolan]

Bought a 22 ft bow rider and hope to take the kids out 8-10 times on Lake Ontario and maybe the same in the upper Niagara or Lake Erie. 

Looking to spend $500 - $700 to get electronics that will be reasonably helpful but easy / intuitive to use. 

What features will be most important to me ? 

Grateful for any insight. 

[Yankee Troller]

I'd stick with a simple Sonar/GPS. Humminbird HELIX 7 is a nice option in that price range.