The world at large would be unfamiliar and mostly unfriendly if not outright dangerous but they are forced to adventure in order to save their village/town or some such equally compelling reason.
None of the party would have ventured beyond the village or at most the next town. All would be personally vested in whatever the quest is and be more focused on achieving that than dealing with any grudges against each other or pursuing personal agendas. Not that they can't also have one or both of those.
Would be using DnD 5e playtest rules starting with the 2nd version and upgrading as new playtests come out. There will be almost certainly the need to occasionally rebuild characters though character concepts shouldn't change and I'll do my best to house rule any changes that overly break concepts so they work.
A few of the games I've gm'd / I am gming:
Living Forgotten Realms - the Sea of Fallen Stars - A number of 4E adventures I ran awhile back.
Broken Mountain Delve - A series of 4E Dungeon Delve adventures I created and ran.
Gruumsh's Eye - 5E solo game about to restart after hiatus.
Come Hell or High Water - 5E game recently started.
Post here if this intrigues you and/or you have any questions, comments, suggestions, or ideas for me.