Get the routine handed over properly, not from memory
Before the animals arrive, ask your friend to write down what they actually do each day: the hay they use, the exact nuggets or pellets and the measured amount, which vegetables these animals already eat, water bottle or bowl, and any quirks such as a guinea pig who only drinks after the bottle is freshly filled. Get the vet's name and address, an emergency contact, and permission to authorise treatment if your friend cannot be reached. Ask what is normal for these individuals, because a sitter can only spot a change against a baseline: how much hay disappears overnight, how lively they are at floor time, and what their droppings usually look like. Keep your friend's own enclosure, bedding, and hide houses if they can travel, since familiar smells settle prey animals faster than new surroundings explained to them.
Set up a quiet guest room away from your own pets
Place the enclosure in a calm room with steady temperature, out of direct sun and away from televisions, washing machines, and the household's busiest doorway. Keep your own animals out of that room entirely for the stay; even the scent and sound of an unfamiliar dog or cat unsettles rabbits and guinea pigs, and direct contact between resident and guest small pets risks both stress and infection. Wash your hands before and after handling the guests, and service their enclosure either first or with separate cloths and tools from your own pets. Give them a day with minimal handling to eat, explore their hide houses, and learn the room's sounds before floor time or lap time begins.
Feed, handle, and watch like the owner would
Keep the diet exactly as handed over, even if you feed your own animals differently; a sudden change of nugget, hay, or vegetables is a common trigger for a gassy, uncomfortable gut in both species. Top up hay little and often so it stays fresh and interesting, refresh water daily, and spot-clean wet bedding so the enclosure smells like itself. Handle guinea pigs on your lap at floor level with both hands supporting the body, and let a rabbit come to you on the floor rather than lifting, since most rabbits feel unsafe in the air and a struggling rabbit can injure its back. Watch eating closely: a rabbit or guinea pig who leaves hay untouched, produces much smaller droppings, or hides through a whole evening should prompt a call to your friend and their vet that day, not the next.
Keep your friend in the loop without fuss
Send a short daily message with a photo, a line on eating and droppings, and anything you changed or noticed. Store medicines or supplements, if any are part of the handover, out of reach and exactly as labelled, and write down anything you give. Keep the enclosure latched and the guest-room door closed as a habit, and brief children in the house on quiet voices and no picking up without an adult. If an animal escapes within the house, close doors calmly, block gaps, and let it come out to a hide box and food rather than chasing it.
Handing them home again
Pass back a short note: how they ate, any off days, how much food is left, and anything that changed in the routine while they were with you. That handover is much easier when the owner's instructions were in front of you the whole stay rather than in a message thread you scrolled through at midnight. KinsLe Care Pass is built for exactly this arrangement, handing a trusted sitter temporary access to a pet's routine and key details so a guest rabbit or guinea pig gets their own care, not a guess at it.