I think at home is better. At least they have more room. Just make sure there's nothing they can get into and there is nothing they could choke on like bones and treats. Maybe even ask MIL to stay there when they're eating to make sure they don't choke.
I'm really confused

I thought when you board the dogs are in kennels all day other than a few potty breaks in the day, no? I also thought someone isn't there during the night or weekends either, no?