Sounds like a blast! Without having any prior info about your nutrition/training, just some thoughts:
Holiday 1 - 4k a day for a week without workouts will probably add a few pounds. If you've been training like an animal leading up to it, it may help some recovery, but even still a week straight of 4k days with no workouts will probably stop having any benefits after 2 or 3 days. If it was me, and I was in a active gaining phase, I'd go down to slightly above maintenance and do some bodyweight work a few times a day if possible, and pick one or two of those days to be a "low day," (lots of protein and fats, very minimal carbs).
I'd also be sure to enjoy my eating and food, just not go overboard. But, I would want to do that to preserve the muscle I've gained and minimize excess fat accumulation. "Bulking" without working out is just "fatting" (adding fat.) But, this mainly depends on your personal preference. If you're ok with adding some body fat on vacation, go nuts. But just make sure you don't convince yourself that eating 4k a day with minimal activity is going add any more muscle than eating maintenance or slightly above maintenance.
Holiday 2 - If you want to make this a "cutting" opportunity, going 4k a day with no workouts during holiday 1 seems counterproductive. Why add on extra fat if you're gonna try to lose it shortly after? Maybe try looking at holiday 1 as a prep for holiday 2. Go to slightly above maintenance calories during holiday 1, do some bodyweight work a couple times a day to keep your metabolism humming along, then when holiday 2 comes around, take advantage of it and try to cut.
To minimize loss of muscle gains, try to bring some servings of MAG-10 in a bag with a shaker cup and pulse throughout the day. Also, making food before hand would be helpful and packing it. Maybe baked oatmeal with lots of protein powder in it, some Metabolic Drive bars, etc. You'll be active all day so hiking, so you'll be burning calories all day. You'll want some carbs for fuel, so don't be carb-phobic during your "cut" week, then lots of protein to preserve muscle, and good fats for fuel (raw nuts are a great, easy, portable choice.)
Good luck and have fun!