In my experience, among Orthodox and Protestants alike, one person leading a prayer at the table is the norm, except at restaurants (though occasionally there too).
When I'm with non-Orthodox people, I pray silently unless I am asked to lead the prayer, in which case I say the Our Father (often the others will join in). It's a prayer everyone is familiar with, and is appropriate for all situations.
When I'm at an Orthodox home, I follow the family tradition. In most homes I've eaten at (both cradles and converts), everyone stands and faces the icons to say the Our Father or sing the troparion if it's a feast day. Then the head of the household (or clergy if present) blesses the food.
So in my experience, the Orthodox "normal" way is to do the whole "concert" thing, but I think among non-Orthodox people there's nothing wrong with saying the Our Father and a short blessing on the food. As Rufus suggested, these prayers were developed in Orthodox cultures and may be a bit much for non-Orthodox people; there's nothing wrong with exercising a bit of personal economia in those situations. I like the Orthodox tradition of standing to pray before the meal, though.