You should be fine for check-in in the First check-in area so long as you are Emerald somewhere or other, though by all means use any other check-in desk open that you see en route, I don't see any added advantage in schlepping past available desks. No issue with guests there.

For Fast Track security in (presumably) South, yes, you are allowed on guest each, so that means you're OK. If you are travelling CE then they can use Fast Track anyway. You can't use the First Wing security since you only have one guest for Gold, unless GGL. But you can both guest in Galleries Club.