It's just 2 of us in the house. If I wanted to halve the recipe.... still use 1 egg?

From the comments at the bottom of the recipe this appears to be a very forgiving recipe. I would be tempted to lightly whisk the egg prior to mixing in and use roughly half the mixed egg at first. If it seems like the cookie "dough" could take more, go ahead and add. Your other option might be to make the full batch, form into the macaroons, freeze half (unbaked) on a cookie sheet lined with parchment, then bagged up, to be baked off at a future date.