I don’t like to rely on repellents. I’d use traps to catch any mice that have found their way into your camper and then focus on mouse-proofing your camper so that more don’t get in. Repellents won’t stop a determined mouse from entering. You need to seal off ALL entry points in your RV, or they will keep coming back. Once that’s done, you won’t have to worry about repellents and whether they are safe for your pets or not.
Here are some tips to mouseproof your camper: https://camperfaqs.com/how-to-keep-mice-out-of-camper-best-methods