I'd add:
take a corkscrew
the bathrooms are tiny
take a couple of large thin towels that you can tuck into the curtain rail to act as curtains. the ones in caravans are usually very thin, so as soon as it is light DC wake up
making the room darker can get you another hour in bed
if it's early in the season, caravans can get cold at night. maybe take a hot water bottle with you to warm the bed
go for simple food - most supermarkets do bags of stir fry veg that you can heat up in a frying pan, or soup is easy to do with some bread
if your DC are young take a couple of bean bags to practice throwing and catching
waterproofs and wellies are essential (unless you are lucky)
take a small box with essentials ie salt, pepper, vinegar, cooking oil, red sauce, sugar, t-bags, matches and a first aid kit.
we've had some brilliant holidays in caravans, in fact dh asked me to marry him in a caravan in Wales