For clarification, and as it was never answered,
A GMRS license IS required, and one license will cover you and your FAMILY.
Retailers don't need any special permission to sell radio equipment, be it GMRS, CB, HAM or Commercial.
Good job finding those at Goodwill. Always nice to find something like that there.
GMRS and MURS are different. GMRS is UHF, MURS is VHF.
As for emergencies, you didn't really give us a lot of info. Are you looking to talk to just your family, or are you looking to talk to others?
If you just want to communicate between family members, then FRS, GMRS or CB would be fine. FRS won't get you very far, though, anywhere for less than a 1/4 of a mile to more, all depending on conditions. A good GMRS radio will get you a bit farther, but don't ever trust the milage claims on the packaging.
MURS would be an option, but it can be difficult to find MURS radios. It's not widely used in most areas, so while it would be difficult to find someone else to talk to, chances are it would be pretty quiet for you and your family to use.
CB might be a good bet to reach others as it tends to be a bit more universally used in SOME areas. Also, since you already have an investment there, why not stick with it?
Amateur radio is great, it gives you a lot of possibilities, however the issue with getting those not interested in radio to get there license is a common issue.