We always leave our dog at a kennel or veterinarian for day care or boarding, picking him up in the late afternoon after a day of sightseeing and meals out. We check out the facilities online and make reservations. I am hesitant to leave our dog in the camper for more than 2 hours maximum, so we mostly day board when we are sightseeing or biking more than 2 hours. This has worked for us for many years. There are usually facilities near national parks or monuments. Worked great this past spring when we were at Scottsbluff NE and Cheyenne WY. And the dog is no worse for wear - he's met some nice people at these places. Good luck!
Rita and her sheltie, Andy