Special Kitty Concerns
Cats do not travel well. They are easily lost and hard to find. Leaving your cat with friends is not always a satisfactory solution. Cats go through an adjustment period in a new environment and this means they will not look upon your friend's house as "home" for quite a while. Your cat will try to escape from a strange house at every opportunity. Leaving your cat home because they are (supposedly) self sufficient is not always safe. Air conditioning can fail in hot weather, illness, loneliness -- all can take their toll on your cat.
Obviously, the most satisfactory arrangement would be to entrust your cat to a boarding facility where security arrangements are adequate to ensure your cat will not escape.
After kitty is picked up from the boarding facility, be sure to keep him locked in at home for a few days before allowing him to roam. He will need to become "at home" again just as he did at the kennel.