IMHO that's an executive level decision. If they think they have the resources (and strategic allies) to properly defend our personnel and sovereign territory (our embassy), then so be it. If there's a tragedy because they don't have the resources, then that's on the executive. (Except, I guess, if your name is Ronald Reagan.)
It would be interesting, and encouraging, if the other guy's faction set up shop outside the embassy to prevent Maduro's people from taking the embassy. Nevertheless, a gauntlet has been thrown down. We will see how far Maduro will go after his ultimatum. He may extend the deadline, with the hopes he doesn't have to take action, but I think that would be unwise. A leader in such a precarious position needs to follow through.