I'd say that I'd press that button immediately. Generally speaking, I'm a very selfless person who puts his loved ones first.
...Problem is, I've never been in a life or death situation before. I've been in intense situations of threat where I haven't backed down in order to protect others, but you never know... You never know what you're really capable of in your darkest hour. Though I don't believe I doubt myself at this moment, there's always that chance that I'm not, or that none of us is, quite as courageous as I claim to be. Troubling, yet true.