It shouldn’t be a problem, nor should your partner make you feel guilty for not wanting to spend every moment with the other folks, although it’s totally fine for her to be with them the whole time if she wants to, since it’s her family and she doesn’t get to see them that often.
The same would be true if the shoe were on the other foot and she was visiting with your family. 5 days is a long time to spend with people that you don’t normally spend that much time with.
It’s the not the amount of time, per se, as much as it is the activities involved and how well you know them. You could spend tons of time, on a regular basis with co-workers, and even though they’re not your family, and you don’t even necessarily like them one way or the other, it’s the activity that you need to do with them that makes it work out reasonably well.
With family, even though they might be great people, because the others aren’t your partner, they’re simply other people who you might like or loathe or have much or little in common with, but you still need to have time to de-compress from them, even if you adore them. Just becaue you’re on vacation, doesn’t mean you don’t need your routines and downtime.
Even when we have relatives come to stay at our house, we always give them time and suggestions as to how they might like to read or watch TV or go for a little walk or talk on the phone or work on their computer, whatever. Doesn’t mean we don’t love them. Hopefully she’ll understand and just have a great time with them. She can just tell them that you’re a little tired or even feeling a bit overwhelmed or that you’re not used to so much excitement.