You know your in-laws the best so you know better what their intentions are and how they would be in this situation.
For example, my in-laws did the same thing with us last year. We go on a caravan holiday every year with our two kids. Last year, my in-laws booked into another holiday park near us for the same week, and they of course did spend some time with us, but they have their own interests too and spent just as much time (if not more) doing their own thing and then just meeting us when it was convenient for both parties. It worked out well for everyone and was nice that the kids got to spend a bit of time with their grandparents (they don’t see them often as they live 3 hours away). It worked out so well, we’re doing the same this year
However, if it was my parents, the opposite would be true. They would want to be staying in the caravan next to us and spending every waking minute with us, but not wanting to do anything we wanted to do and not helping with the kids - actually it would be more like having an additional two kids on holiday with us
So if they’re more like my parents, then no, you’re not being unreasonable!
If they’re more like my in-laws though, then maybe just roll with it and see how it goes - it might turn out better than expected!