My parents have a house near Charleston, and I've been many times. It's great, I love it. I will say, July is extremely hot and humid. For that reason, I would stay near the beach during that time of year, it will probably be 10 degrees cooler with a nice breeze. Isle of Palms is a nice area, and is very close to the city itself, maybe 15 minutes. It's pretty residential, without a lot of activities or restaurants, etc., but is relaxing and has a nice beach. You have easy access to all that is in Charleston itself, plus even closer than that is Mount Pleasant, which is a suburban area that has tons of restaurants and shopping. Folly Beach is also great. It is still quiet, but has some cute restaurants and shops and a nice pier. It's a little farther away, maybe 30-40 minutes from the city, but still totally do-able for experiencing both places. I've stayed in Isle of Palms when I was a teenager, and in Folly Beach a few years ago. My parents live in Mount Pleasant, so now that they have the house there we obviously stay there, and drive to Isle of Palms to go to the beach, which is only like 4 miles away. Let me know if you have specific questions!
That's awesome suzv, that's a great central location to take advantage of both the beach as well as the city and surrounding area. I hope you have a great time!