One of the things that we have found helpful when travelling with our kids is to top and tail our kids in their bed: one with their head up one end, the other with their head up the other. It does require a little bit of rearrangement of the bedclothes, but it does mean that they sleep better.
Of course, we'd prefer for them to have their own separate single beds, because sleep comes much more easily that way, but sometimes there's only a double bed for them.
We find that separating their heads and legs means that they are less likely to bump into each other in the night. Because neither of them is particularly tall, it means that much less of them "overlap" in the same section of bed.
And of course if they sleep better, they're much less grumpy the next day. Great when you're wanting to enjoy travelling with kids, rather than just tolerating it!