not close but if you're headed north
There's a great boarder in Beltsville, MD called Paradise for Pets (they also breed golden retrievers there). Normally we head north on vacation so, even though they are far, it's not inconvienent as we drop off the dogs on the way.
They have very large, grassy outdoor kennels as well as indoor kennels in case of bad weather for the dogs. Also, if you want, they will put your dog in a large kennel with similar dogs for a short period of time. For example, we have a young rottie and an old greyhound. The greyhound doesn't want anything to do with any other dogs. So when we board them, we have the rottie spend time with other rotties. The dogs love it there and we were so impressed with the setup we've modeled our outdoor kennel similar to theirs. Every other boarder we've seen had cement-only outdoor runs, not large grassy areas.