Sometimes the single beds collapse and one goes under the other, which is worth knowing. A pool noodle can go under the sheet to form a basic guard to stop a toddler rolling out of bed. If you take a bed guard in the future, make sure it will fit narrower 2ft6 beds, which are usually what are in caravans.
Consider taking a travel blackout blind (or just some blackout fabric, cut some small holes in and buy some lick and stick hooks to put on the window, or take some pegs and peg it to the top of the existing curtains).
Really useful boxes are useful as baby baths plus you can easily pack in your stuff to take on holiday too. Alternatively, we just put the shower on very low and cool-to-warm and gently showered DD. She got used to it.
Be careful installing a pressure stair gate as the walls aren't usually very sturdy, neither are the door frames. Just go steady when installing. We kept the front door locked at all times but basically went out every day (and wore the kids out so they slept all night).
We take a slow cooker for meals. Gas pressure can be low at peak times and I've always found the oven takes longer to cook. We put the slow cooker on in the morning so we have something ready for dinner when we got back.
PIL have their own caravan, so we've done a fair few holidays in it with both kids. Luckily it's large and we only stay on our own there.