I personally would recommend Long beach although its further to get to by dolmus. Its a lot bigger than ladies beach and there is a lot more to do for kids. Most of the hotels provide entertainment for the kids at nighttime as well. Bar street is great for the likes of yourselves at nightime but might be a bit too much for a seven year old. Try the old part of town where its a lot quiter but still good craic.
I'd recomend ladies beach for nightlife with your family..there is a real family orientated feel to the area... lots of nice bars, where you can sit outside & watch the sunset, listen to some music and have a nice cold drink!!