I always send Theo with plenty of chewable toys he can destroy like willow balls etc which he can play with and take frustration at not being free roam on when he goes to a sitter. Do you have a cool pod to send with them? Fans are good just make sure your friend places it somewhere where the bunnies can escape the breeze if they want to. you could
Also ask them to put ice cubes in the water a couple of times a day and run a cold cloth over their ears if they are too warm. They will be annoyed at not getting out as much as they are used to but they will be fine for one week – just a temporary situation! I would bag their food for each day separately so your friend doesn’t have to measure it out so they get exactly as much as they are used to. Bagging their veg might not be practical as you’re away a week but let your friend know what veg they normally eat and how much. I would send plenty of their Normal hay with them too to kee as much the same as possible – I usually just send a whole 1kg pack for a week. You could send some teddies/blankets that smell of their home to help them settle. Let your friend know their normal behaviours and what behaviours might suggest that something is wrong. Provide your friend with details of your normal vet and of your pet insurance if you have it in case of emergency. Most of all – relax ? They have each other which will help them settle and they will be fine!