Family plan & VT, MA, PA coverage

The rest of my family is considering joining the mobile phone age. Two major questions:

1) Is it worth considering a family plan if we're all grown up and scattered across the Northeast? The family consists of:

- Me. Currently a Verizon customer, joined last year when I was in Boston. I'm in our family vacation house in Greensboro, VT (edge of the NE Kingdom near Hardwick) for the year. I don't really get service here at the house so I only use the phone when on the road and use very few minutes these days. Next year I'll be somewhere else not yet determined.

- My parents. Live south of Philadelphia. I actually don't get the best reception in their house but it's decent. They are mainly looking for a phone for emergencies and for when my father travels (eventually they may get more hooked).

- My sister and her husband. Live in Boston. They would each want a phone.

It seems like the advantage of the family share plan would be that it could be significantly cheaper, especially since at least initially I don't think any of us would be using our phones much at all (especially once you exclude IN calling and nights/weekends). The disadvantage is obviously that only one person would get the bill so we'd have to work out paying for it. But we're a pretty close family. My sister and her husband, though, may decide they want the independence. Are there significant costs or problems with breaking up a family share plan into individual plans if it doesn't work out? Are there cheaper plans than Verizon if my sister and husband want to go on their own?

1) Coverage and choosing a provider.
I'm assuming that most providers would be decent in Boston and Philadelphia. Everyone spends significant time in our house in Vermont. I don't think any company provides great reception in Greensboro, but reception in the surrounding areas would be nice, as well as any info on future coverage of Greensboro. Also, good coverage along the highways used to get here would be nice (I-93 through NH and I-91). I originally chose Verizon because I was told they had the best coverage for VT/NH, is that still the case? If my sister and husband go off on their own are there other companies they should consider? My sister as an interest in Working Assets, which contracts with Sprint, but I get the impression that Sprint coverage in VT is not good.

Another considerations for coverage would be the places where my father travels for business. Most often Princeton, New York, Washington, and Mississippi. In addition to info on these locations, are there other places in the US we should be aware of where Verizon coverage really falls short?

Thanks for any help,

MNH