I would say 5 months is plenty old enough to take to the groomer. I have questions about the practice of allowing all the dogs to interact. There are more people that we realize who do not keep their dogs' vaccines up-dated. How does the groomer handle that issue? Also, I would take my baby in and maybe have nails clipped or a sanitation cut done while I watched out of the puppy's sight. See how things go and work from there. I am not sure why the dogs have to stay all day. How about you, Yorkie Rose? You groomed for a hundred years..