The most I've spent alone with both kids is approximately an hour.
Tomorrow, I've got the whole morning. WonderWife™ is going out and doing stuff. I owe her for letting me do the same last week.
I know all of you "experienced parents" out there are laughing at my trepidation (including you WonderWife™!), but I know it's going to be a rough morning (cue more laughter).