We have had real good luck with Verizon, but it won't cover your unlimited data requirement. In fact, I don't know of any carrier that still has unlimited data and has any kind of nation wide coverage. I am fortunate to have unlimited on my two Verizon cards, but I have had them since they first came out (PCMCIA cards :) ).
I think you need to have a look at where you travel mostly and find the best coverage. You are going to be stuck with 5GB limits, so best to get the best coverage. I am using two data plans, and we have never gone over our 10GB (theoretical) limit. We use a load balanced router to keep them loaded equally.
The reason I mention coverage is that some companies are truly covered in some areas. They will advertise it, but will use roaming on someone else's towers. Much time doing that and they will drop you. I found this in Kansas - no Verizon towers where we went, and was in roam all the time.
Your phone will be tough, but for your wife, possibly the phone I currently have would work. I have a Samsung Rogue and have been happy. Slide out keyboard is great. Real good camera. Cheap data plan.
Of course, whatever phone you decide on will depend on what carrier you go with. I suggest going to EVDOinfo.com or 3Gstore.com to do your research. Ping EVDOalex here on the site. He is very knowledgeable with multiple carriers.
Good luck!
kev