I've been to Hyannis many times, I've never seen anything like the above poster has described.
I hadn't until about a month ago. There are some shops and restaurants but it's not a place I'd feel comfortable with kids. PTown was a long time ago, so I can't be certain.
Bay View Campground is on the Cape side of the bridge in Bourne along Rt 28 a couple of miles beyond the bridge.
Ooops. Bad memory. You are correct.
Bay probably warmer.
This I know for certain-hubby grew up with a family cottage in Sandwich. Bay side is colder. If you want a "warm" beach try Monument Beach. Regardless water temps will be very chilly that time of year unless we have a warmer-than-normal spring that MIGHT bring water temps up a bit.