I went through the SAME problem. I was 15 lbs from my goal and ran up against a vacation. I phased off and went to phase 3 for 2 wks before vaca.
It ended to be a big mistake for me. My experience was not great. Those 2 wks slowly became 2 wks of cheating. Then my vacation on top of it. Although I didn't follow phase 3 like I should have, I still have HUGE concerns that phase 3 has any physiologic weight stabilizing effect. And believe me...I have researched it
Here is what I think...phase 3 is key for psycological reasons only. A way to slowly introduce carbs and a new way of eating after a diet of rapid weight loss. Any stabilization effect is from psycological reasons alone.
The fact is, after ketosis goes away, water weight WILL be gained. It isn't possible to keep the water weight off without being in ketosis. Also, as your glycogen is replenished w/carbs, your glycogen stores will add on a few lbs too. The reason some still don't see a weight gain while in phase 3 is because you may still be losing fat stores as phase 3 is still calorie resticted.
So the scale may stay the same as you gain water and glycogen and lose a bit more fat. But I just cannot find any other scientific explanation for why IP leaders suggest that phase 3 seals the deal so to speak. It is not a magic phase where all your efforts will be sealed if you do it for 2 wks before cheating.
It is never popular to go against IP recommendations, but with the science in mind...long story short...I personally would stay on track RIGHT UP TO YOUR VACA. Then have a cheat day(s) followed by as many protein days as you can possibly fit it
I would bet you will gain the least weight this way. Have a great time!