I haven't ever done dog boarding ... which is why we NEVER go away!!!
I would look for somewhere that looked like a home from home situation .. my ex sister-in-law ran her own dog boarding business just as a hobby really. She would only take one or two dogs at a time, but they would live with her in her house as if it were their second home. I can't tell you how many times the dog didn't want to go home when their owners came to collect them!!!