This is a very difficult situation and It's hard to know how you could have done anything more than you did.  Sadly, these people did not treat you well and I see no way to completely recoup your losses.

However (and this may sound crazy and flippant, but I mean it to be a note of encouragement) I predict you will have a wonderful vacation in someone else's home!  We had booked our airfare and the same day our rental manager had taken a 4 day reservation during our 3 week time in our house.  We ended up renting a neighboring house and having a "real" vacation at our locale for the first time in years -- no maintenance, no worries!  It reminded us of why we had purchased a home there in the first place.

I hope things settle down and that you have a wonderful time.  And maybe you can get a last-minute rental!

I figured it might be useful to revisit a  response written in reply to a question posted by a fellow homeowner who was having serious problems with a barking dog, and even more with the hard-headed owner: When can I make a guest leave?  Her situation was different from yours, in that the guest had paid for the time period, but was making life insufferable.  The question she asked, however, is the same as yours.  Here are some thoughts I then offered her, relevant to your situation:

Sorry to hear about your "dog" of a tenant.  I... first want to strongly encourage you to at least consider  taking action, A,S.A.P.

To do so, it might be helpful to have a bit more  information on what  your rights might actually be.  While my opinion is  only that, I am an  attorney, and during my own ordeal did some  research  and spoke with  police to evaluate my options.

On a personal level: as stressful as you might find  the idea of confrontation (and I fully  understand and empathize,  believe me), my experience has taught  me that,in the long run, going  through with it might wind up inflicting less damage than failing to  stand  up for yourself, and allowing this guest to disrespect you and  your  neighbors.

Just take stock of yourself, and ask yourself honestly if  the situation will leave you angry long after the guest has moved on to  her next victim.  Everyone is different, and your life is your own.  So  I would never presume to speak in terms of what you MUST, or even should do. Rather, I offer a few thoughts so you might better understand the  range of options at hand, and what your basic rights may be. Bottom  line: my focus is upon your basic question,When can I make a guest leave?  And the answer is, whenever you decide to, and are ready to follow through.

Oh, and also to offer this always-needed reassurance: You are not alone. Do hang in there.

Now, about your rights: you do NOT simply have to put up with it.   I learned that our "transient rental" situation is not to be confused  with traditional home occupancy in this important sense: the latter  requires court involvement and a formal eviction proceeding to get them out.

Our situation is different, and so is the “bundle of rights" at our disposal.  In the eyes of the law we are more like operators of a hotel, or  even for that matter a restaurant, that (as you'd imagine) can, if  necessary, simply call the police and say "These people are trespassing,  they have been put on notice, and they need to LEAVE." A home  resident's right of occupancy depends upon a lease or rental agreement,  which can be enforced only through a court of law.  The right of a guest  to remain in a transient rental, in contrast, depends strictly upon   their abiding by the stated "rules of the house."  If they do not, they have become "trespassers," and you have the right to put them on  notice of such, and ask them to leave. 

(Note, too, that we are certainly deserving of some privileges,  as traditional landlords need not collect or remit State and County sales taxes on rental proceeds each month, and we do.)

I'm not suggesting that you necessarily should pull out  the heaviest artillery first, for a number of reasons.  Some people  just aren't thinking, and the experience might be redeemable.  By all  means, see if you can work it out.  Offer another solution first, if  possible.  And, always try your level best not to act in anger. 

PS  I like the idea of the msdebj’s Power of Attorney, but I’d be wary of even making reference to the word “eviction,” for fear of confusing a transient stay with a more formal leasehold interest.  I would use the word “removal” instead, perhaps.