Before you leave, you need to let your grandparents watch how you care for your rabbit, how and what you feed him, and how to clean up after him, and let them help so that they will know the routine. If you want them to be able to get Yogi out of his cage and back in, make sure that they can do that. Do they need to lure him back in with a treat, or do they have to pick him up? Make sure that they know how to correctly pick up and hold a rabbit if that is needed. Ask them if they have any questions about his care.
Besides giving them a hands on lesson, write down his daily diet and routine and any care tips that you might need to share.
Make sure that they have the name and phone number of your vet in case any medical problems arise.
Also make sure that they know to keep the cat out of your room.
I assume that you have air conditioning in your room since you are in a hot climate. Make sure that your grandparents are aware of how your rabbit normally acts, and that they will know if something may be off with him that might require medical attention. I also assume that they will be able to call you if they have any questions or concerns.