I personally send my clients a verbal update the evening that their dog got dropped off, the following morning to let them know how they did overnight with a picture and then picture/update every 2-3 days. I don't feel like sending a ton of pictures is really nessisary. I always get one really nice picture on my big camera to give them for their first booking that I add to my wall of client dog pictures in my dog room. My clients always appreciate that.

Personally, when I go on vacation I don't want to be bothered and I feel like a lot of people feel the same way. If it is a sitter you have used for multiple bookings you should trust that if there is anything wrong they will contact you. I guess I'm just the no news is good news kind of person.