My son is 12 and daughter is 7 and they still sleep in the sleeper together at times. We do prefer the 1bd with the sleeper chair, but when we don't book it, they have to make do. They haven't complained...yet. Maybe because they know it wouldn't matter. They get what they get.
But I will admit that I started researching a solution when I had to sleep with my daughter one night - she was 6 and we were in a regular hotel room and the beds were only doubles so I was afraid that there wasn't enough room for my son and her to sleep together since I always put a divider (pillow) between them. I thought it would be fine and I would cuddle with her....seems harmless enough.
Anyways, within an hour of my daughter falling asleep, she would make sudden movements - she would be fast asleep but would suddenly kick or swing her arms. By morning I hadn't slept a wink. I mentioned it to husband and son and they started laughing at me.

They thought it was strange that I was at the very edge of the bed while my daughter was curled up in a cosy ball. They were not aware of what transpired over night.
My son did mention it but he didn't make such a big deal about it so I didn't think it was that bad. I guess he got used to it and just slept through it.
So, I would like to get a solution as well since I don't think my son should have to be
subjected to her crazy sleeping habits.
The strange thing is that at home, she sleeps quite calmly...I guess she's just more comfortable with having her own bed. A few times when we have the sleeper chair, she would be in the sleeper sofa and when I check on her she hasn't moved at all. I suppose she just doesn't like anyone sleeping with her.