I assume they are outdoor rabbits then, alot live ondoors these days.
Mine is indoors and with that brings danger with them getting out escaping from their cage or run and chewing though an electric cable.
Whether their indoors or out, have you any pets that could be a danger to the rabbits or a neighbour have a 'uncontrollable' pet, some dogs can be very agressive and can kill a rabbit. Have you any wild animals that could be a risk ....foxes?
Alway make sure they have clean water, staple food and hay. Fresh food is not massively import, put some in carrot apple - no pips, but remember to look for uneaten fresh food when you go back next time and remove it, this stops insects being attracted to it and stops the animal eating rotten old food, carrot is the most hardy food and lasts longer in the cage, apple goes all brown very quickly.
Make sure if the rabbit is outside that it has shelter from the weather, not in full sun and is weatherproof.
I think the main basic fact to remember is to alway remember to lock them in properly, if you are at all worried about them getting out add and extra lock or catch, or place some thing heavy infront of the door.