I love a real tree. If you want to ahve that sensation in your home, and plan to do it at Thanksgiving, you will still get several weeks of enjoyment before you travel. But I would get a smaller one, so it is easier to take down the day or 2 before you travel. You will already be busy with travel prep, so make sure this fits into the plans (a smaller one would make it go quicker).
But as the daughter of a lifelong firefighter..and sister of a current one...I agree with a previous poster...H&LL NO. Do not leave it up while you are gone. Why risk it? And who wants to come home to all of that extra work and mess? Personally I would prefer to have it all cleaned up before I go on my holiday trip, as I always feel I need a vacation from my vacation! I would do a much smaller floor tree and set aside a few hours to put it all back where it goes before I leave!
Have a fun trip!