If you already have a family plan and you're renewing, you can do that through Amazon. I did, even kept my legacy 1000 minutes for $70 plan.
Nope, Amazon has it's own contracts and they don't have the family plan. You're going to have to go with Verizon it appears. They do have a bogo though, at least last week there was one.
Same here. My wife's phone purchased through Amazon simply added her to our legacy plan. When I called to activate the phone, the VZW couldn't find the new purchase. Asked where I purchased the phone. Told her from Amazon. She said, "OK. Got it." No other difference.