HELP - received job offer right before big vacation

I have a significant 2 week abroad vacation planned and booked. I'm leaving in one week. The problem is that I just received a great job offer and they are looking for an immediate decision. The trip is already booked and approved. 

I really like my current employer and don't want create a negative impression on my way out (Despite being severely underpaid). Hoping to keep them as references and not burn bridges. So what are my options here?

What is the most professional way to approach this? The way I see it I have two options, neither of which are ideal. 

- Give them a month's notice now and work one week, take the 2 week vacation, then work one final week when I get back. 

- Not tell them anything and give my two weeks notice as soon as I return from vacay (I don't like this option - this seems worse for the company because they lose out on 3 extra weeks to hire a replacement and I also have to work an extra week on the tail end, but the pro is I don't look like a shithead for announcing that i'm leaving and then going on vacation for 2 weeks a week later before getting my affairs in order)

Really appreciate any advice.